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-The Project Gutenberg eBook of More Minor Horrors, by Arthur Everett
-Shipley
-
-This eBook is for the use of anyone anywhere in the United States and
-most other parts of the world at no cost and with almost no restrictions
-whatsoever. You may copy it, give it away or re-use it under the terms
-of the Project Gutenberg License included with this eBook or online at
-www.gutenberg.org. If you are not located in the United States, you
-will have to check the laws of the country where you are located before
-using this eBook.
-
-Title: More Minor Horrors
-
-Author: Arthur Everett Shipley
-
-Release Date: November 13, 2021 [eBook #66726]
-
-Language: English
-
-Character set encoding: UTF-8
-
-Produced by: Peter Becker, Les Galloway and the Online Distributed
- Proofreading Team at https://www.pgdp.net (This file was
- produced from images generously made available by The Internet
- Archive)
-
-*** START OF THE PROJECT GUTENBERG EBOOK MORE MINOR HORRORS ***
- Transcriber’s Notes
-
-Obvious typographical errors have been silently corrected. Variations
-in hyphenation have been standardised but all other spelling and
-punctuation remains unchanged.
-
-Italics are represented thus _italic_.
-
-
-
-
- MORE MINOR HORRORS
-
-
- [Illustration: Mosquitos in the Colvith River delta, Arctic Alaska,
- about 71° lat., July 1909. The Eskimo, Natkusiak, had stood still for
- a minute or two, and refrained from brushing them off, while loading a
- uomiak. (From the _American Museum Journal_.)
- [_Frontispiece_]]
-
-
-
-
- MORE
- MINOR HORRORS
-
- BY
-
- A. E. SHIPLEY, Sc.D.
-
- HON. Sc.D. PRINCETON, F.R.S.
-
- MASTER OF CHRIST’S COLLEGE, CAMBRIDGE, AND READER IN ZOOLOGY
- IN THE UNIVERSITY
-
- ILLUSTRATED
-
- LONDON
-
- SMITH, ELDER & CO., 15 WATERLOO PLACE
- 1916
-
- [All rights reserved]
-
-
-
-
- EDMUNDO ALFREDO CARRINGTON
-
- ET
-
- JOHANNI TRISTRAM YARDE
-
- COLLEGII CHRISTI DILECTISSIMIS ALUMNIS
- HUIC AB ORIENTI ILLI AB OCCIDENTI PARTE
- PRO PATRIA PUGNANTIBUS
-
-
-
-
- PREFACE
-
-
-My publisher tells me that this volume will be regarded as a sequel
-to ‘The Minor Horrors of War,’ and he assures me that sequels are
-not a success. I have no doubt my publisher is right, because if
-publishers were not invariably right, and authors invariably wrong, how
-can one explain the fact that publishers are proverbially prosperous
-and prominent people, whereas authors are notoriously penniless and
-obscure? In spite of his warning, however, I propose to publish this
-little volume, for there still ‘air some catawampous chawers in the
-small way, too, as graze upon a human pretty strong’—as ‘one of them
-inwading conquerors at Pawkins’s’ called them—that were unmentioned in
-my earlier book.
-
-I am indebted to the kindness of the Editor and Proprietors of the
-_British Medical Journal_ for permission to reprint Chapters I to IX
-and Chapter XI, and to the Editor of _The Journal of Economic Biology_
-for permission to reprint the twelfth chapter, of this book, and I
-offer them my thanks. I also thank Mr. Hugh Scott (the University
-Curator in Entomology), and Professor G. H. Carpenter of the Royal
-College of Science, Dublin, for much kindly help.
-
- A. E. SHIPLEY.
-
- CHRIST’S COLLEGE LODGE, CAMBRIDGE,
- _April 1916._
-
-
-
-
- CONTENTS
-
-
- CHAPTER PAGE
-
- I. COCKROACHES (_Periplaneta_) 1
-
- II. COCKROACHES (_continued_) 16
-
- III. THE BOT- OR WARBLE-FLY (_Hypoderma_) 25
-
- IV. THE MOSQUITO (_Anopheles maculipennis_) 42
-
- V. THE MOSQUITO (_continued_) 53
-
- VI. THE MOSQUITO (_continued_) 65
-
- VII. THE MOSQUITO (_continued_) 76
-
- VIII. THE MOSQUITO (_continued_) 86
-
- IX. THE YELLOW-FEVER MOSQUITO (_Stegomyia
- calopus_) 101
-
- X. THE BISCUIT-‘WEEVIL’ (_Anobium paniceum_) 111
-
- XI. THE FIG-MOTH (_Ephestia cautella_) 114
-
- XII. THE STABLE-FLY (_Stomoxys_) 124
-
- XIII. RATS (_Mus_ or _Epimys_) 135
-
- XIV. THE FIELD-MOUSE (_Apodemus sylvaticus_) 153
-
- INDEX 161
-
-
-
-
- ILLUSTRATIONS
-
-
- FIG. PAGE
-
- A portrait of the head of an Eskimo attacked by
- mosquitos _Frontispiece_
-
- 1. _Periplaneta orientalis_, male, dorsal view 2
-
- 2. _P. orientalis_, male, side view 6
-
- 3. Mouth parts of _P. orientalis_ 9
-
- 4. _P. orientalis_, female, dissected 10
-
- 5. Egg capsule of _P. orientalis_ 12
-
- 6. Cast skin of the nymph stage of cockroach 18
-
- 7. Nymph stage of cockroach escaping from old skin 19
-
- 8. _Hypoderma bovis_ 29
-
- 9. Eggs of _H. lineatum_ 33
-
- 10. Eggs of _H. bovis_ 35
-
- 11. Entrance hole of _H. lineatum_ 37
-
- 12. Cow being chased by warble-fly 40
-
- 13. Side-view of head of _Anopheles maculipennis_, female 44
-
- 14. Section through proboscis of _A. maculipennis_, female 45
-
- 15. Piercing-lancets of _A. maculipennis_, female 46
-
- 16. _A. maculipennis_, female, sucking blood 58
-
- 17. _A. maculipennis_, male 66
-
- 18. Stridulating organ of _A. maculipennis_ 70
-
- 19. Larva and eggs of _A. maculipennis_ 78
-
- 20. Side view of the head of larva of _A. maculipennis_ 81
-
- 21. Under surface of head of larva of _A. maculipennis_ 82
-
- 22. Diagrams of mosquitos and gnats 85
-
- 23. Side view of pupa of _A. maculipennis_ 91
-
- 24. Tail of pupa of _A. maculipennis_ 93
-
- 25. Imago mosquito issuing from pupa-case 95
-
- 26. _Stegomyia fasciata_, female 104
-
- 27. Larva and eggs of _S. fasciata_ 106
-
- 28. Larva of _S. fasciata_ 107
-
- 29. Egg of _S. fasciata_ 108
-
- 30. The biscuit-‘weevil’ (_Anobium paniceum_) 112
-
- 31. The larval and pupal stages of _A. paniceum_ 113
-
- 32. Orchard of fig-trees 115
-
- 33. The fig-moth (_Ephestia cautella_) 116
-
- 34. Figs drying on reeds 119
-
- 35. Figs packed on strings 120
-
- 36. Pile of refuse-figs 122
-
- 37. The stable-fly (_Stomoxys calcitrans_) 125
-
- 38. _Stomoxys calcitrans_ 126
-
- 39. Wings of _Musca domestica_ and of _Stomoxys calcitrans_ 127
-
- 40. Side view of head of _Stomoxys calcitrans_ 128
-
- 41. _Stomoxys calcitrans_. Eggs 129
-
- 42. Acephalous larva of _Stomoxys calcitrans_ 130
-
- 43. Coarctate pupa of _Stomoxys calcitrans_ 131
-
- 44. The rat (_Mus rattus_) 136
-
- 45. Head of _Mus rattus_ 138
-
- 46. _Mus decumanus_ 143
-
- 47. Head of _Mus decumanus_ 145
-
- 48. The field-mouse (_Apodemus sylvaticus_) 156
-
- 49. Diagram of burrow of field-mouse 159
-
-
-
-
- MORE MINOR HORRORS
-
-
-
-
- CHAPTER I
-
- COCKROACHES (_Periplaneta_)
-
-
- PART I
-
- _The Governess:_ And, perhaps, Mabel, as they are not black
- and as they are not beetles, you will in future call them cockroaches.
- _Mabel:_ Certainly, Miss Smith, although they are not cocks
- and they are not roaches. (_Punch._)
-
-
-In ‘The Minor Horrors of War,’ we rather neglected the Navy—the
-senior Service, and till now the more dominant of our two magnificent
-forces—partly because it is less interfered with by insect pests than
-is the sister Service, though the common pests of our poor humanity—the
-flea, the louse, the bug—are, like the poor, ‘always with us.’ Like
-aeroplanes, insects have captured the air; like motors, they have made
-a respectable show on land; but they have signally failed at sea. They
-have nothing corresponding to battleships or submarines; and a certain
-bug, called _Halobates_, alone hoists the insect flag on the ocean, and
-that only in the warmer waters.
-
- [Illustration: FIG. 1.—_Periplaneta orientalis_, male. × 2. Dorsal
- view. 1, Antenna; 2, palp of first maxilla; 3, prothorax; 4, anterior
- wings; 5, femur of second leg; 6, tibia; 7, tarsus; 8, cerci anales;
- 9, styles. (From Kükenthal.)]
-
-Insects are not only highly intelligent animals, but are by far the
-most numerous and dominant class of the Animal Kingdom; and they have
-probably come to conclusions about themselves and the sea, comparable
-to those expressed by Dr. Johnson about man and the ocean: ‘To all the
-inland inhabitants of every region the sea is only known as an immense
-diffusion of waters, over which men pass from one country to another,
-and in which life is frequently lost.’
-
-But one insect at least causes more trouble to sailors than to
-soldiers—and that is the cockroach. Like the bed-bug, the cockroach
-came into England at the end of the sixteenth century, and, like the
-bed-bug, it came from the East. It seems to have been first introduced
-into England and Holland in the spacious times of Henry VIII by the
-cross-sea traffic, and from about the end of the sixteenth century the
-cockroach began gradually to spread throughout the Western world. Like
-the rat, the bed-bug, and the domestic fly, it has become thoroughly
-acclimatised to human habitations, and is indeed an associate of man.
-It is very rarely found living apart from some form or other of human
-activity.
-
-This insect seems to have been first described in England in
-Moufet’s ‘Insectorum Theatrum,’ 1634, and he speaks of it as living
-in flour-mills, wine-cellars, &c., in England, and he tells us how
-Sir Francis Drake took, in 1584, the _San Felipe_, a Spanish East
-Indiaman, laden with spices and burdened with a great multitude of
-flying cockroaches on board.
-
-This species was _Periplaneta orientalis_; but there is another and a
-larger species, which presumably came into England from the West later
-than its Eastern cousin _P. americana_—which can frequently be seen in
-England running about in the cages in our zoological gardens—but it is
-not on exhibition, it is a by-product, and is not counted in the fee
-for admission to the gardens.
-
-Latter tells us there are ten species of BLATTODEA which occur in
-Britain; but only three of these are indigenous, and these three all
-belong to the genus _Ectobia_. _Ectobias_ are smaller than cockroaches,
-and do not frequent human habitations, but live in shrubs, under
-rubbish heaps, &c. Some species of _Ectobia_ are, however, very
-destructive and have been known to destroy in one day the whole
-accumulation of dried but not properly salted fish in a Lapland
-village. Of the remaining species of cockroach most are local, and
-occur sporadically in particular factories, or places where food is
-stored but they are not very widely spread.
-
-As we have said above, _P. orientalis_ is the common English cockroach,
-_P. americana_ occurs especially in zoological gardens and menageries;
-but a third species, _P. germanica_, sometimes gets established.
-Mercifully, _P. germanica_ does not seem to spread. Neither _P.
-germanica_ nor _P. americana_ seem to make much headway against _P.
-orientalis_, which appears to be predominant over both these other
-species.
-
-_P. germanica_ is probably most methodical, very thorough, very
-brave, very faithful—but rather lacking in the power of understanding
-the point of view of others. If it has any association with its
-specific name, it illustrates the most striking example in the world’s
-history of the divorce of wisdom from learning. ‘O Lord! give us
-understanding,’ should be the prayer of _P. germanica_.
-
-Miall and Denny tell us that from the first introduction of _P.
-orientalis_ into England it took two centuries before it spread far
-beyond London. In 1790 Gilbert White speaks of it as ‘an unusual
-insect, which he had never observed in his house till lately,’
-and, indeed, at the present moment many English villages are still
-blissfully ignorant of this particular nuisance.
-
-As Fig. 2 shows, the cockroach is a somewhat slackly put
-together insect. One might almost call it rather slatternly and
-loose-jointed—and the latter it certainly is. Its head moves freely on
-the thorax, and the thorax on the abdomen. The successive segments
-of the latter move very freely on one another. The legs are long and
-mobile, and so are the antennae with which the animal is ceaselessly
-testing the ground over which it flits hither and thither in its
-restless activity.
-
- [Illustration: FIG. 2.—_Periplaneta orientalis_, male. × 2. Side
- view. 1, Antenna; 2, head; 3, prothorax; 4, anterior wing; 5, soft
- skin between terga and sterna; 6, sixth abdominal tergum; 7, split
- portion of tenth abdominal tergum; 8, cercianales; 9, styles; 10, coxa
- of third leg; 11, trochanter; 12, femur; 13, tibia; 14, tarsus; 15,
- claws. (From Kükenthal.)]
-
-Cockroaches are very difficult to catch. They practically never walk,
-but run with a hardly believable rapidity, darting to and fro in an
-apparently erratic mode of progression. Even when caught they are
-not easily retained, for they have all the slipperiness of a highly
-polished billiard-ball. They have great powers of flattening their
-bodies, and they slip out of one’s hand with an amazing dexterity.
-Besides their slipperiness they have another weapon, and that is a
-wholly unpleasant and most intolerable odour, which is due to the
-secretion of a couple of glands situated on the back of the abdomen.
-The glands which produce this repellent odour are sunk in the soft
-membrane which unites the fifth and sixth abdominal segments, and
-the moment a cockroach is attacked it exudes a sticky, glue-like
-fluid, which gives out this most unendurable smell. The fluid is
-extraordinarily tenacious and difficult to remove from the hand of
-those who have touched the insects. No doubt the cockroach, in nature,
-finds safety in this from the attacks of insectivorous animals.
-
-Cockroaches, as has been said, very rarely walk, they nearly always
-run, and they advance the first and third leg of one side at the same
-time as the middle leg of the other, pulling themselves forward with
-their front legs and pushing themselves forward with the hindermost.
-They are thus constantly poised on a tripod. They occasionally, but not
-very often, use their wings for flight. When they do so, their anterior
-wings are stretched out at right angles to the body, and take no active
-share in beating the air. They act in effect as monoplanes. It is the
-hinder wings which really do the active flying. After a flight, the
-hinder wings are shut up something in the manner of a fan.
-
-The flattened coxae, or thighs, of the leg are adapted for shovelling
-débris back from beneath the body when the insect is enlarging its
-habitation. When the cockroach gets into a dusty ‘_milieu_’ the dust
-is immediately removed; the hairs on the legs act as clothes-brushes
-and brush every part of the body, whilst the antennae, which attract
-any dust in the neighbourhood, are repeatedly drawn through the closed
-mandibles and so cleaned. A cockroach is able to walk on smooth
-surfaces because it possesses between the joints of the tarsus certain
-soft, white patches, very velvety, and these give the creature a good
-hold, and prevent slipping even on glass.
-
-Cockroaches will eat pretty well everything. They are a great nuisance
-on board ship, where they are said to gnaw the skin and nibble the
-toe-nails of sailors. Hardly any animal or vegetable substance
-is absent from their menu. It is said that they will even devour
-bed-bugs, and that natives on the African shores, troubled by these
-semi-parasites, will beg cockroaches as a favour from sailors in
-passing ships.
-
- [Illustration: FIG. 3. Mouth appendages of _Periplaneta_ (magnified).
- A, Mandible. B, First maxilla: 1, cardo; 2, stipes; 3, lacinia; 4,
- galea; 5, palp. C, Right and left second maxillae fused to form the
- labium: 1, submentum; 2, mentum; 3, ligula, corresponding to the
- lacinia; 4, paraglossa, corresponding to the galea; 5, palp. (From
- Latter.)]
-
-The mandible (Fig. 3), with its strongly toothed surface, is capable
-of biting and grinding into fragments a very varied diet. The food is
-moistened by the secretion of the salivary glands, which is capable of
-converting starch into the more soluble sugar. The food is further
-ground up by a series of hard ridges projecting into the inner face of
-the gizzard (Fig. 4, 7). The secretion of the so-called hepatic caeca
-is capable of emulsifying fat and rendering proteins soluble. Thus the
-ordinary food substances are reduced to a condition in which they are
-capable of diffusing from the lumen of the alimentary canal into the
-blood which floods the body cavity.
-
- [Illustration: FIG. 4.—A female cockroach, _Periplaneta_, with the
- dorsal exoskeleton removed, dissected to show the viscera. Magnified
- about 2. 1, Head; 2, labrum; 3, antenna, cut short; 4, eye; 5, crop;
- 6, nervous system of crop; 7, gizzard; 8, hepatic caeca; 9, mid-gut
- or mesenteron; 10, Malpighian tubules; 11, colon; 12, rectum; 13,
- salivary glands; 14, salivary receptacle; 15, brain; 16, ventral
- nerve cord with ganglia; 17, ovary; 18, spermatheca; 19, oviduct;
- 20, genital pouch, in which the egg-cocoon is found; 21, colleterial
- glands; 22, anal cercus. (From Latter.)]
-
-The external movement—one might almost say ‘the panting’—which is very
-obvious in the abdomen, the alternate flattening and deepening of
-this part of the body, is a movement of inspiration and expiration,
-the air being driven into the stigmata and so into the tracheae or
-breathing-tubes. There is a considerable variation in the rate of these
-pulsations, but the cockroach’s heart beats at an average rate of
-seventy to eighty contractions per minute.
-
-Although cockroaches have fairly developed eyes, they seem to trust
-very largely to tactile impressions in appreciating their relations
-to the surrounding world. Their antennae and the palps of their first
-and second maxillae are constantly touching the surface on which they
-are resting or moving, and from time to time their antennae wildly
-wave in the air in a manner which suggests that they are smelling out
-the external circumstances which environ them. The 39,000 sensory
-‘nerve-endings’ which are found in the antennae of the male cockroach
-are almost certainly olfactory in function. At the posterior end of
-the body the two ‘cerci’ are also sensitive to tactile impressions, and
-probably act at the hinder end of the cockroach as the antennae act at
-the forward end. Cockroaches are certainly keenly sensitive to light,
-and, as every one knows, they shun the light, and when detected in
-daylight or candle-light they make as quickly as they can for some dark
-hole or crevice in which to hide.
-
- [Illustration: FIG. 5.—Egg capsule of _P. orientalis_ (magnified). A,
- External view; B, opened; C, end view. (From Miall and Denny.)]
-
-Cockroaches breed during the summer, and their eggs are laid in packets
-of sixteen in a capsule or cocoon with rounded ends, and with an upper
-corrugated edge. These cocoons are very like the little hand-bags
-ladies have carried since the dressmakers denied them pockets. There
-are sixteen ovarian tubes in the female, and each of these deposits
-one egg in each cocoon. The ventral portion of the seventh abdominal
-segment in the female is shaped like the prow of a boat, and it is in
-this structure that the cocoon, or egg-case, is built up. Each egg is
-fertilised by a spermatozoon which has been deposited by the male in
-the spermatheca of the female. The eggs are placed in a double row,
-eight in each row, facing each other, and, as they gradually develop,
-it becomes apparent that the ventral face of one row faces the ventral
-face of the other row—just as the little choir-boys on the Gospel side
-of a chancel face the little choir-boys on the Epistle side, but much
-nearer together—and that their heads are all directed towards the
-corrugated ridge.
-
-They are at first quite white, but with large black eyes, and it
-has often struck me how surprised they must be when they awake
-to consciousness and find themselves staring at a brother or
-sister cockroach just opposite, of whom they have had hitherto no
-consciousness. The ripe embryos secrete some fluid, probably saliva,
-which dissolves the ridge, and it is through this dissolved or softened
-ridge that they ultimately make their way into the outer world.
-
-Young cockroaches are very active, running about and seeking everywhere
-for any food of a starchy nature. They are, in fact, miniatures of
-their parents, for a cockroach, like many of the primitive insects, has
-a direct development, and there are no such stages as caterpillar and
-pupa in their life-history.
-
-But, like other insects, cockroaches change their skin from time to
-time, and they lose little time before beginning this ecdysis, for
-they first cast their cuticle immediately after escaping from the
-egg-capsule. The second ecdysis is four weeks later, and the third at
-the end of the first year, and after this time they moult annually. At
-the seventh moult, when the animal is now four years old, it assumes
-the form of the perfect insect, and is capable of reproduction. The
-later moults fall in the summer time, and so does fertilisation and
-oviposition. Male cockroaches may be distinguished from the females by
-their well-developed wings and wing-covers. They stand higher on their
-legs than do the females, whose abdomens often trail upon the ground.
-
-In spite of the noxious secretion of their abdominal glands there are
-creatures who habitually feed on cockroaches—hedgehogs, for instance,
-are frequently imported into our houses to check these pests. Rats,
-cats, polecats, frogs, and wasps have been known to eat them, and some
-few of the digging-wasps lay them down in their larders for the use
-of their progeny. Some birds will also tackle them. But even the most
-devoted friend of cockroaches can find little to say in their favour,
-except that they are currently reported to form the basis of the
-flavouring of a very popular sauce; but even wild cockroaches will not
-drag from me what the name of that particular sauce is.
-
-
-
-
- CHAPTER II
-
- COCKROACHES (_Periplaneta_)
-
- PART II
-
- In Russia the small Asiatic cockroach (_P. orientalis_) has everywhere
- driven before it its greater congener (_P. germanica_).
- (DARWIN, _Origin of Species_.)
-
-
-Cockroaches do a very considerable amount of damage by consuming
-food-supplies. But they do not stop at food-supplies: woollen clothing,
-newspapers—not a really great loss—blacking, ink, leather, and even
-emery-paper, are all to their taste, and, being of an economical frame
-of mind, they devour their own cast skins and the dead bodies of their
-relatives. The late Professor Moseley recorded how on one occasion,
-when on the circumnavigating tour of H.M.S. _Challenger_, a number of
-cockroaches took up their abode in his cabin and devoured parts of his
-boots, ‘nibbling off all the margins of leather projecting beyond the
-seams on the upper leathers.’ He further records:—
-
- One huge winged cockroach baffled me in my attempts to get rid of
- him for a long time. I could not discover his retreat. At night he
- came out and rested on my book-shelf at the foot of my bed, swaying
- his antennae to and fro, and watching me closely. If I reached out
- my hand from bed to get a stick, or raised my book to throw it at
- him, he dropped at once on the deck, and was forthwith out of harm’s
- way. He bothered me much, because, when my light was out, he had a
- familiar habit of coming to sip the moisture from my face and lips,
- which was decidedly unpleasant, and awoke me often from a doze. I
- believe it was with this object that he watched me before I went to
- sleep. I often had a shot at him with a book or other missile as he
- sat on the book-shelf, but he always dodged and escaped. His quickness
- and agility astonished me. At last I triumphed by adopting the advice
- of Captain Maclear and shooting him with a pellet of paper from my
- air-gun, a mode of attack for which he was evidently unprepared.
-
-It is on record that cargoes of cheeses have been destroyed by
-cockroaches on ships. Not only did they devour great quantities of each
-cheese, but they defiled every one of them with their very tenacious
-fluid which has, as we have noted above, a most disgusting smell. This
-the cockroaches poured out from their stink-glands, making the cheeses
-of no commercial value.
-
-When a cockroach casts its skin a median longitudinal slit appears
-on the back of the thorax, and through this slit the insect slowly
-emerges. With much labour and difficulty it squeezes its body through
-and pulls one limb after another from its old integument, until at last
-even the long whip-like antennae are completely withdrawn. Certain
-portions of its inner anatomy—such as the lining of parts of the
-breathing-tubes, or tracheae—are also withdrawn. Should the discarded
-skin not be eaten by the emergent insect, it remains on the floor, and
-might easily be mistaken for a sedentary cockroach but for the fact
-that live cockroaches never are sedentary.
-
- [Illustration: FIG. 6.—Cast skin of older nymph (pupa). × 2½. (From
- Miall and Denny.)]
-
- [Illustration: FIG. 7.—Nymph (in last larval stage) escaping from old
- skin. Magnified. (From Miall and Denny.)]
-
-The incomplete metamorphosis, the generalised character of the nervures
-of the hind wings, the complete separation of the three thoracic
-segments (or rather their want of that fusion so conspicuous in the
-higher insects—the flies and the bees) and the undifferentiated
-condition of the mouth parts—all point to the insect being of a
-primitive type. But there is no doubt that, whether a primitive
-insect or not, the cockroach is a very successful one; it is an
-_arriviste_—as ‘our lively friend, the Gaul,’ to quote Mr. Micawber,
-would say—probably owing to its attaching itself in all cases, and
-with unvaried devotion to the habitation of men. Not popular with
-humanity, it nevertheless ceaselessly extends its domain by slowly yet
-surely entering into new and hitherto unconquered human habitations.
-In spite of insect-traps and vermin-killers, it is extremely difficult
-to eradicate from a house when once it is well established. It has, in
-fact, gradually dislodged in most places in Great Britain and Ireland
-the old domestic house-cricket. For in spite of its irritating, and to
-some people quite maddening, ticking, the ‘cricket-on-the-hearth’ has
-somehow established itself as a household pet, and one that has won not
-only our respect but our affection. So curious is our psychology.
-
- The cockroach has many enemies, and the genus _Sphex_ (or _Chlorion_)
- may be seen hunting about here and there, up and down the road-side
- and gardens, searching for its favourite prey. It spies out a
- cockroach, which appears to know intuitively that there is danger at
- hand, for it shows symptoms of great fright, and seems so confused
- that it cannot run away. The _Chlorion_ pounces upon the insect,
- clasps it with its mandibles between the head and the corselet, and
- stabs it in the body with the sting. Then it flies off for a little
- distance, and awaits the effects of the poison thus introduced; and
- when the convulsions of the victim have ceased, the clever little
- insect seizes its stupefied prey, and drags the heavy burden with
- great efforts to its nest. Usually the opening of the cavity is so
- narrow that the cockroach cannot be got in, for its legs and wings
- stick out and prevent its introduction. But the _Chlorion_ sets to
- work and cuts off the legs and the wings, and having thus lessened
- the difficulty, it strives hard to push the body into the hole; but
- as this plan usually fails, the hymenopteron enters first of all,
- seizes the cockroach with its mandibles, and drags it in with all its
- force. As the integuments of the _Blatta_ are more or less soft and
- flexible, the great insect is at last forced into the gallery, where
- it never could have been expected to have entered. Such proceedings on
- the part of the _Chlorion_ almost verge upon the domain of reason; and
- it is difficult to explain them by the notion of that very indefinite
- quality called instinct, for the manœuvres vary according to the
- circumstances, and there appears to be an intelligent method of
- overcoming every difficulty.[1]
-
-Apart from animals which eat it, there are a number of parasites
-which infest it, beginning with the parasitic beetle _Symbius
-blattarum_, whose wingless females attach themselves to the bodies
-of the cockroaches and feed upon their tissues. Then occasionally a
-round-worm, _Filaria rhytipleurites_, whose sexual stage is passed
-in the rat, is found in its larval stage in the fat bodies of the
-cockroach.
-
-Two years ago Dr. C. Conyers Morrell undertook some investigations
-and observations as to what part, if any, cockroaches played in the
-dissemination of pathogenic microbes, his object being, as he says,
-‘first to ascertain what bacilli belonging to the colon group are
-likely to be conveyed to food and milk by this insect, and secondly
-to find whether known bacteria and moulds can be transmitted by the
-faeces.’ Dr. Conyers Morrell’s experiments were conducted on one of the
-Union Castle liners sailing to South Africa, and the insects which were
-investigated were collected only from the larder or passages adjacent
-to the kitchens; in no case were they taken from lavatories or from
-staterooms. The general condition of the ship, which was almost new,
-was one of exceptional cleanliness, and thus afforded good conditions
-for the experiments. Dr. Morrell was of opinion that there was little
-danger except by contamination from the faeces of the infected insect.
-
-[1] _The Transformation of Insects_, by P. M. Duncan. London: Cassell,
-Petter, Galpin and Co., 1882.
-
-One of his first experiments was to prove that should cockroaches
-fall into the dough which was being baked for bread the heat of the
-baking entirely destroyed the bacilli that were in the alimentary canal
-of the insect. With regard to infection with the colon bacillus, he
-kept an infected insect under the best antiseptic conditions he could
-compass until it had passed some undigested food. Of this undigested
-food an emulsion was prepared, and cultures were made from it on
-bile-salt medium and in litmus-milk. Afterwards special cultures were
-made in gelatine and peptone solutions. Incubation was conducted in
-all cases at 37° C., and cultures were made from seventeen specimens.
-Five of these produced colonies of bacilli on the bile-salt medium,
-with sub-culture results as follows: Four produced acidity and
-clotting of milk, acid, and gas in glucose, lactose, and saccharose,
-and production of indol. But the bacilli did not liquefy gelatine,
-and were Gram-negative. One specimen produced gas in glucose and
-lactose, and liquefied gelatine and coagulated milk. The former in its
-reaction corresponded to the _Bacillus lactis aërogenes_, the latter to
-_Bacillus cloacae_. In five cases greenish moulds of the _Aspergillus_
-variety were found after inoculating litmus-milk.
-
-Cockroaches will devour human sputum with avidity, and are frequently
-to be found in spittoons (or, as the more delicately minded American
-calls them, ‘cuspidors’[2]), and it is interesting to know that after
-feeding the insects on infected sputum from a tuberculous patient, the
-tubercle bacilli are found in the faeces within twenty-four hours; two
-specimens which had been fed on staphylococci showed these pathogenic
-organisms in their faeces and in the cultures on agar-agar, which were
-obtained from their dejecta.
-
-I have quoted largely from this important paper, and now propose
-to quote a good deal more, and thus I append Dr. Conyers Morrell’s
-conclusion of the important experiments he conducted on the Union
-Castle liner.
-
-[2] From the Portuguese ‘cuspidor.’ Cf. the Latin ‘conspuere.’
-
-The foregoing experiments, though insufficient in number to afford a
-basis for working out percentage results, are, I think, of some value,
-in that they prove the following facts:—
-
-The common cockroach is able by contamination with its faeces (1) to
-bring about the souring of milk; (2) to infect food and milk with
-intestinal bacilli; (3) to transmit the tubercle bacillus; (4) to
-disseminate pathogenic staphylococci; (5) to transmit from place to
-place destructive moulds.
-
-These facts, taken in conjunction with the life-habits of the insect,
-lead to the conclusion that the cockroach is able to and may possibly
-play a small part in the dissemination of tuberculosis, and in
-the transmission of pyogenic organisms; that the insect is in all
-probability an active agent in the souring of milk kept in kitchens
-and larders; and that it is undoubtedly a very important factor in
-the distribution of moulds to food and to numerous other articles,
-especially when they are kept in dark cupboards and cellars where
-cockroaches abound. The distribution and numbers of the cockroach are
-rapidly increasing, and unless preventive measures are adopted the
-insect is likely in the course of time to become a very troublesome and
-possibly a very dangerous domestic pest.[3]
-
-[3] _British Medical Journal_, 1911, ii. 1531.
-
-
-
-
- CHAPTER III
-
- THE BOT- OR WARBLE-FLY (_Hypoderma_)
-
- Apropos de bottes.—(REYNARD.)
-
-
-Britain wants many materials in this war, and as long as our back
-door is open we are getting them. Petrol, rubber, zinc, copper,
-molybdenum, vanadium, thorium, nickel, saltpetre, wool, cotton,
-are all coming to us in greater—immeasurably greater—quantities
-than those in which they can filter through neutral countries into
-Germany. These things count. The shortage of leeches in Great Britain,
-on which I have already dwelt, is negligible, and is entirely
-over-balanced by the really serious shortage of sausage-skins in
-middle Europe. I am told that our meat-salesmen at Smithfield
-were offered an incredible advance on the normal rate for these
-products—so-very-necessary-and-under-no-circumstances-to-be-done
--without-with-casements—but the meat-salesmen at Smithfield were
-patriots. In their dire extremity the Germans have been trying to make
-them of cellulose.
-
-Amongst the things both combatants most want is leather. One of the
-most impressive efforts we non-combatants have been watching, since
-August 1914, is an army growing, near us and next us, with apparently
-an unlimited supply of leather belts, leather trappings, leather
-saddlery—leather harness for man and beast. Yet they tell me that
-the price of leather since the War began has appreciated by 140 per
-cent. This may be so; but, as Joseph Finsbury remarked in ‘The Wrong
-Box,’ ‘there is nothing in the whole field of commerce more surprising
-than the fluctuations of the leather market. Its sensitiveness may
-be described as morbid.’ But Joseph was no business-man, and kept in
-the background of the office a capable Scot who was understood to
-have a certain talent for book-keeping. Readers of Stevenson will
-remember that nobody had ever made money out of Finsbury Brothers,
-Leather-merchants, except the capable Scot who retired (after his
-discharge) to the neighbourhood of Banff, and built a castle with his
-profits. There are still many capable Scots about, and this may, to
-some extent, account for the present price of Sam Browne belts.
-
-There must have been well over 150,000 Sam Browne belts made since the
-War began. A widespread belief—at any rate, amongst the junior members
-of the Army—is that Sam Browne was an American; possibly some slight
-confusion existed in their dear young minds between the inventor of the
-belt and John Brown whose ‘body lies,’ &c. The inventor of this useful
-cincture was, however, Sir Samuel James Browne (1824-1901), G.C.B.,
-K.C.S.I., the well-known Indian fighter, who lost an arm, and gained a
-V.C. by his gallantry during the Mutiny. He was for a time the military
-member of the Governor-General’s Council, and he commanded the first
-division of the Peshawar Field Force during the Afghan War of 1878-9.
-The 22nd Regiment in the Indian Army, a frontier force, is known as Sam
-Browne’s Cavalry.
-
-The belt was first used unofficially, but it gradually found favour
-with the authorities, and it is mentioned officially in the regulations
-drawn up for the Straits Settlements in 1891, and for Egypt and West
-Africa in 1894. It was only on April 24, 1900, that the pattern was
-‘sealed,’ and adopted as a general item of equipment for all officers
-on Active Service.
-
-Anything that seriously destroys the continuity of the integument of
-our oxen, which interferes with the ‘wholeness’ of the hide which is
-the basis of leather, clearly affects—and affects detrimentally—an
-important munition of war. The bot- or warble-fly does this. But
-it does more: its attacks materially lessen the value of the beef
-which potentially lies beneath the hide, and thus in a double sense
-the warble-fly is the enemy of man whether he be soldier or sailor.
-Further, its attacks seriously lessen the milk-supply of the country.
-
-Amongst the numerous families into which the true flies (DIPTERA) are
-divided, none are more harmful to human enterprise than that of the
-_OESTRIDAE_, or bot-flies, inasmuch as every single species and every
-single member of this family passes its larval stage within the tissues
-of some vertebrate host, and frequently in those of domesticated
-cattle; sometimes even in man himself. One of the commonest genera
-of this family of flies is _Hypoderma_, which is represented in our
-islands, and in many other parts of the world where domesticated cattle
-are reared, by two species—_H. bovis_ and _H. lineatum_, both commonly
-known as bot- or warble-flies.
-
-The harm caused by these larvae, living as they do in the tissues of
-the body, beneath the skin, by piercing holes through the integument or
-skin, whereby they make their exit from the ‘warble’ or subcutaneous
-tumour in which they have passed their latest larval stage, is almost
-incalculable.
-
- [Illustration: FIG. 8.—_a_, _Hypoderma bovis_; _b_, maggot of _H.
- bovis_; _c_, egg of _H. bovis_; _d_, puparium of _H. bovis_; _e_,
- egg of _H. lineatum_; _f_, maggot of _H. lineatum_; _g_, _Hypoderma
- lineatum_. All the figures are magnified. (From F. V. Theobald’s
- _Second Report on Economic Zoology_, British Museum, 1904.)]
-
-Miss Ormerod, who for so many years kept alight the lamp of economic
-entomology in England, published some statistics on this subject
-towards the end of the last century. In 1888, out of slightly over
-100,000 hides dealt with in the Newcastle cattle and skin market,
-60,000 were ‘warbled,’ and the loss to the trade amounted to £15,000.
-The same year at Nottingham 8500 out of 35,000 hides were largely
-spoiled; at Manchester 83,500 out of 250,000 suffered from the same
-cause: the losses in these towns being estimated for the year in
-question at about £2000 and £17,000 respectively. Taking the average
-from all sources in England, Miss Ormerod estimated the fall in value
-at from 5s. to 6s. on every warbled hide. The most riddled hides—that
-is, those with the most punctures—come to the sale-room during April
-and May, but the trouble extends from February to September.
-
-There is also the loss caused by the warble to the butcher—and through
-the butcher to the Army Service Corps. The presence of the fly-larva,
-which is quite a large creature, induces chronic inflammation in the
-tissues, and a state of things known to the trade as ‘licked beef,’
-and unless the meat-salesman cuts away the affected parts the meat is
-unsaleable in the market, or greatly depreciated in value. The average
-loss to the butcher on a warbled carcass is estimated at 6_s._ 8_d._
-
-Finally there is a loss to the stock-raiser and dairy farmer. We shall
-have occasion later to refer to the curious psychological effect the
-warble-fly has upon the cattle, causing them to ‘gad’ or stampede
-in wild gallops, which interferes with fattening, deteriorates the
-milk-supply, and is especially injurious to cows with calf. Mr. Imms,
-in his most useful summary of the warble-fly, tells us that the loss
-due to _H. lineatum_ in America is calculated at 28 per cent. of their
-total value of all the cattle in the States. Some authorities place
-the total loss to the agricultural community in England at £2,000,000,
-others at £7,000,000, a year, whilst others estimate that the loss
-amounts to about £1 sterling on every head of horned cattle.
-
-Curiously enough, the fly itself is rarely seen, and still more rarely
-taken. Mr. Imms records only two specimens of _H. bovis_ in the
-collections of the British Museum, and but fifteen of _H. lineatum_. A
-similar scarcity of imagos in public collections obtains on the other
-side of the Atlantic, where for many years the last-named species
-was alone recognised. Two years ago, however, Dr. Hadwen, working in
-Canada, established the widespread existence of _H. bovis_ in the
-Dominion; almost certainly it also occurs in the States; but Dr.
-Hadwen had to send to Dublin for specimens with which to confirm his
-find. None existed in the collections in Ottawa, and a ‘request for a
-specimen ... from the Bureau of Entomology at Washington, D.C., could
-not be granted owing to a scarcity of specimen’! These statements are
-interesting, since at present the tanneries of Canada are working night
-and day to help our shortage in leather at home.
-
-_H. bovis_ measures ⅝ in. in length, _H. lineatum_, somewhat less
-robust, ½ in.; the hairy covering of the last named is of a foxy red
-at the tail end, while that of _H. bovis_ is yellow, both at the tail
-end and towards the front of the body. The flies are most abundant
-during July and August, though they are believed to occur throughout
-the summer. At Athenry (co. Galway) _H. lineatum_ is common by the
-middle of May. They fly very rapidly, and are difficult to follow with
-the eye. They rejoice in warm, sunny weather, and remain in retirement
-during cold or cloudy days. Hadwen describes the egg-laying by the
-female ‘as a sort of frenzied process, the fly striking’ with its
-ovipositor twenty or thirty times rapidly, then leaving the animal for
-fifteen minutes or so, when the process was repeated. The eggs are
-attached one at a time to the hairs of the cattle and very close to the
-base of each hair, not near the tip, where the horse bot-fly deposits
-its ova. The eggs of _H. bovis_ are scattered and isolated; those of
-_H. lineatum_ are arranged in rows of some seven or more half-way up
-the hair and are contiguous. The favourite region for placing the
-eggs is on the hock and on the back of the knee, or on the thighs and
-flanks, and hence the American cowboys call the insect the ‘heel-fly.’
-Undoubtedly by standing with their legs in water the herd is delivered
-from the pest—at any rate, for the time.
-
- [Illustration: FIG. 9.—Eggs of _H. lineatum_, attached to hair of cow.
- Five of the eggs are hatched and six unhatched. Magnified 15 times.
- (From Carpenter, Hewitt, and Reddin, _Journ. Dept. Agric. Ireland_,
- xv., 1914.)]
-
-The eggs are large, 1·25 mm. in length, and enclosed in a whitish
-shell, which is prolonged behind into a brownish foot, and this foot,
-which exudes some sticky excretion, adheres to the ruminant’s hairs.
-The foot of the egg-shell, in fact, consists of two lobes or valves,
-which clasp the hair between their sticky inner surfaces.
-
- [Illustration: FIG. 10.—Eggs of _H. bovis_ attached to hairs. Note
- attachment near base. Slightly enlarged. (From Hadwen.)]
-
-Within the egg the youngest of the four larval stages is maturing. When
-hatched it is less than 1 mm. long, but it is ‘a terror for its size,’
-being armed with a formidable spine and two hooks in the mouth, and
-with rows of strong spines on all the body-segments. Later, we find
-a second stage, very much smoother and less spiny than the first and
-this lies within the tissues of the host, embedded in its muscles and
-membranes, notably in the submucous coat of the gullet; and now the
-question confronts us, which once confronted George III apropos of
-the apple in the apple dumpling, ‘How the devil did it get in?’ There
-seems to be with _Hypoderma_ but two possible modes of entrance into
-the body of its host—that is, domesticated cattle: (1) The eggs, or the
-newly hatched larvae, are licked up by the tongue, as are the eggs of
-the horse bot-fly—and this might be held to explain the not infrequent
-occurrence of the second larval stage in the walls of the oesophagus;
-or (2) the larvae bore their way directly through the skin. From
-experiments carried on for several years which show that cattle unable
-to lick themselves are not protected from warbles, Professor G. H.
-Carpenter of the Royal College of Science, Dublin, concluded that the
-larvae do not enter by the mouth. During the summer of 1914, he and his
-able assistant, the late Mr. T. R. Hewitt, definitely proved that ‘the
-newly hatched maggot does bore through the skin of cattle’; probably
-after an ecdysis they find their way to the submucous coat and muscles
-of the gullet, and here for a while they rest. I quote from the account
-of Carpenter and Hewitt some of their most crucial experiments carried
-out at the Athenry and Ballyhaise Stations of the Irish Department of
-Agriculture:—
-
- In July 1914, twenty-four maggots were hatched in the incubator, and
- some of these were used for observations as to behaviour when placed
- on a calf’s body. Glaser, in 1913, had tried to carry out observations
- of this kind by placing maggots on a shaved portion of a calf’s skin;
- he found that they made no effort to bore through. Instead of being
- shaved, a small patch of the shoulder of one of the Ballyhaise calves
- was clipped, so as to have the conditions as normal as possible, when
- newly hatched maggots of _H. bovis_ were placed on it. Immediately
- they started crawling down the clipped hairs to the skin, and, as soon
- as they reached the surface, they began to burrow. On account of their
- small size it is hard to discern them, but by carefully watching
- through a lens it was seen that they enter perpendicularly to the
- surface, evidently cutting into the epidermis with their mouth-hooks
- and occasionally bending their bodies. Mr. R. G. Whelan, A.R.C.Sc.I.,
- Superintendent of the Ballyhaise Agricultural Station, kindly helped
- in the observations and confirmed them. Six hours after being placed
- on the calf, the maggots disappeared completely. Next morning the
- spots where they had entered were marked by little pimples, like
- those of the Athenry animals, easily to be seen with the naked eye.
- These increased slightly in size, but soon healed up, and in less
- than a week not a trace of the maggots’ entrances could be found. The
- boring-in of the maggots seemed at first to cause the calf a little
- pain, but the symptoms of discomfort soon passed away.
-
- We have still to find out what happens to the first-stage larva after
- it has bored into the skin and how far it travels before it undergoes
- its first moult. Gläser found that some eggs of _H. lineatum_ laid
- on his trousers hatched, and that a maggot bored right through into
- his own skin. From symptoms of swelling and pain in various regions
- he concluded that this maggot travelled to his gullet, and he finally
- extracted it (in the second stage) from his mouth.[4]
-
- [Illustration: FIG. 11.—Entrance hole of _H. lineatum_ maggot into
- the skin of a cow. The hairs around the hole have been clipped short.
- The white incrustation is due to a discharge from the hole, which has
- hardened. Magnified 12 times. (From Carpenter, Hewitt, and Reddin,
- _Journ. Dept. Agric., Ireland_, xv., 1914.)]
-
-Perhaps in the first stage they may be carried by the blood stream.
-They seem in their second larval stage to wander freely through the
-tissues, especially through the muscular tissues, of the body of
-their host—usually working upwards, and not infrequently reaching the
-neighbourhood of the vertebral column before taking up—still in the
-second larval stage—their final position, where their presence gives
-rise to the ‘warbles,’ or subcutaneous cysts or tumours, in which the
-third and fourth larval stages are passed.
-
-[4] _The Irish Naturalist_, October 1914.
-
-It seems odd that an insect pest, which so seriously affects our supply
-of leather, of meat, and of milk, should have been studied for over a
-century and yet conceal its chief secret from man. But the problem is
-much more difficult than the layman thinks.
-
-Whatever be the route the maggot travels through the body of the calf
-or cow, by the spring the fourth larval stage—when it is about an inch
-long, and perhaps half as much in breadth—is reached in the ‘warble’
-or cyst, under the skin. Here, nourished by the products of the
-inflammation it sets up, and breathing by two spiracles at the hinder
-end of its body, which are directed to the opening of the ‘warble’
-which it has pierced through the skin, the larva rests until one fine
-morning it pushes its way, aided by its stout bristles, through the
-opening and tumbles into the outer world.
-
-Apparently it does not think much of its new surroundings, for it loses
-no time in hiding under some clod of earth or stone or crevice in the
-soil, and straightway turns into a dark brown pupa or chrysalis. This
-stage lasts three to four weeks, and then the perfect fly emerges, and
-will soon be ready to lay her eggs on some new victim.
-
-[Illustration: FIG. 12.—Cow being chased by fly. Note terrified look of
-eyes. (From Hadwen.)]
-
-As a rule it is the yearlings who suffer most, and then the
-two-year-olds; the older cattle being comparatively immune. The
-inexplicable terror which the warble-fly induces in its victims is
-testified to on all hands, but has never been adequately explained.
-_Hypoderma_ does not bite, neither does it sting. Many other
-blood-sucking insects, whose puncture must involve some pain, are
-tolerated by cattle with a flick of the tail, or are frightened off by
-a gesture of the head; but the presence of the warble-fly induces a
-mysterious fear which rapidly spreads through a herd, and results in
-a general stampede—often referred to by cattle-breeders as the ‘gad.’
-This terror communicates itself even to the ‘stalled ox,’ and cattle
-confined within cowsheds show symptoms of extraordinary unrest when the
-fly is abroad amongst their kin in the pastures. The resulting evils
-are, of course, far graver in the unlimited prairies of the West—the
-great cattle-breeding districts of the United States and Canada—than in
-our carefully hedged or fenced meadows. A great many ‘dips,’ ointments,
-and chemical solutions have been recommended for the prevention of
-the grubs in cattle, but none have proved entirely satisfactory. The
-tedious method of removing the grub from the tumour is the only safe
-one. This can be done by the mere pressure of the fingers when the
-grub is nearly mature and ready to leave its host, or by the use of
-small forceps should the grub be young and recalcitrant. Once removed
-the grub should be immediately destroyed, and some such antiseptic as
-coal-tar applied to the lips of the vacated tumour.
-
-
-
-
- CHAPTER IV
-
- THE MOSQUITO (_Anopheles maculipennis_)
-
- PART I
-
- Where the water is stopped in a stagnant pond,
- Danced over by the midge.
- (R. BROWNING, _By the Fireside_.)
-
-
-There is no zoological distinction between a mosquito, a gnat, or
-a midge. But, as a matter of convenience, we might confine the
-term ‘gnat’ to the genus _Culex_, the term ‘mosquito’ to the genus
-_Anopheles_, and the term ‘midge’ to the genus _Ceratopogon_ and its
-congeners, whose collocation with the naked knees of the Highlander is
-said to have given rise to the ‘Highland Fling.’
-
-There is no doubt about it that both the mosquito and the gnat are
-extraordinarily beautiful insects. This fact, however, has been veiled
-from the public partly owing to their small size and more especially
-because of their irritating bite, which causes the sufferer to kill
-a mosquito at sight rather than examine its fairy-like beauty or its
-fascinating dances in the air, far surpassing in grace and agility
-anything seen in the Russian ballet. But biting is the dominating note
-of a mosquito, and we may as well consider, to begin with, how it bites.
-
-If we examine the head of a mosquito we shall find that it is shaped
-like a circular cushion bearing two enormous eyes—so large that in the
-male they touch above the forehead and almost meet below the chin. Each
-eye consists of hundreds of facets of a brilliant green hue, set in
-a darkish background, like emeralds arranged on a black surface. The
-head also bears a quantity of hairs and flattened scales whose number,
-shape, and arrangement are of considerable systematic value.
-
-The following are the appendages of the head:—
-
-1. A pair of antennae, which are markedly different in the two sexes.
-
-2. A pair of mandibles. These are absent in the male.
-
-3. A pair of first maxillae, each of which has a jointed tactile palp.
-
-4. A pair of second maxillae which have fused together to form a deeply
-grooved soft process in which the other appendages lie.
-
-Beside these four pairs of appendages, which are in reality modified
-limbs, there are two median processes, which project one from the
-top, the other from the bottom, of the mouth, like elongated and
-hardened upper and lower lips. These are the median labrum above—a
-deeply grooved structure whose edges approximate and almost touch, thus
-forming a tube along which the blood of the victim is sucked. Lastly,
-there is the hypopharynx—sometimes termed the tongue—a median structure
-a double-edged sword, rising from the bottom of the mouth, and it is
-this that is the cause of all the trouble.
-
- [Illustration: FIG. 13.—Side view of the head of a female _Anopheles
- maculipennis_ (magnification about 20), with the various mouth
- parts separated, but in the relative position in which they lie
- when enclosed in the groove of the labium. This figure shows the
- characteristic cephalic scales, _a_, Antennae; _cs_, cephalic scales;
- _cl_, clypeus; _lxe_, labrum + epipharynx; _mn_, mandible; _hp_,
- hypopharynx; _mx_, first maxilla; _li_, labium; _mp_, maxillary palps.
- (From Nuttall and Shipley.)]
-
- [Illustration: FIG. 14.—Transverse section through the middle of the
- proboscis of a female _Anopheles maculipennis_, showing the relative
- position of the parts when at rest. Two tracheae and two pairs of
- extensor and flexor muscles are seen in the labrum. _lxe_, Labrum +
- epipharynx; _tr_, trachea; _mus_, muscles; _hp_, hypopharynx; _sal_,
- salivary duct; _mx_, first maxilla; _mn_, mandible. (From Nuttall and
- Shipley.)]
-
-A glance at Fig. 13 will show how these various mouth appendages
-can by a skilful use of dissecting needles be separated out, but in
-nature they are all packed together in a case; the arrangement in the
-case is shown by Fig. 14, which represents a transverse section of
-the proboscis. The term ‘proboscis’ is given to the totality of all
-these structures taken and packed together. With the exception of the
-labium and of the tactile maxillary palps all the mouth appendages
-lance into the skin. The proboscis of the male is, however, too weak
-to pierce the human integument, and it is the female which does all
-the damage. When a mosquito is going to bite, she alights so gently
-that her approach is unperceived, and she proceeds to thrust her
-arsenal of weapons into the epidermis of her victim almost unfelt; the
-feeling comes later. These weapons are all guided, by the forked end
-of the softened labium, just as one’s finger-tips guide the end of
-a billiard-cue. These ‘mouth parts’ are exceedingly fine, extremely
-sharp-edged structures, whose consistency is about that of whalebone,
-and both the mandibles and the maxillae have a toothed, serrated edge
-(Fig. 15). They are partly pushed in by muscles in the head, partly,
-I think, by the lowering of the body, and they sink slowly and surely
-into the flesh with as much ease as a paper-knife will penetrate a
-cream-cheese. But as they sink deeper and deeper into the integument
-the body of the mosquito approaches nearer and nearer to the skin of
-the victim, and the labium is pressed farther and farther backwards
-until at the end of a satisfactory puncture the distal and proximal
-parts of the labium are parallel and touching.
-
- [Illustration: FIG. 15.—A side view of the labellae and
- piercing-organs of the proboscis of a female _Anopheles maculipennis_,
- dissected out to show the tips of the mandibles, maxillae, and labrum
- + epipharynx. The hypopharynx is not shown, _li_, Labium; _lxe_,
- labrum + epipharynx; _mx_, first maxilla; _mn_, mandible; _la_,
- labellae. (From Nuttall and Shipley.)]
-
-It is rather an interesting point that the labium does not enter the
-skin, because the larvae of certain _Filarias_—one of which produces
-elephantiasis in man, and the other severe heart trouble in the dog—are
-found in pairs—probably a male and a female—in the labia of mosquitos.
-How exactly these nematode larvae leave the labium of the mosquito, and
-enter the body of the man and the dog, has not definitely, I believe,
-been cleared up; but that they do enter the human and the canine skin
-seems certain.
-
-We have mentioned that the labrum is a grooved tube with its edges
-practically in proximity, and it is up this tube that the blood of the
-bitten is sucked by the well-known suctorial pharynx which occupies so
-large a part of the interior of the head of a mosquito. Much the most
-dangerous weapon of the whole armoury, however, is the hypopharynx.
-This is shaped like a double-edged sword with a very minute groove
-running down the centre; this groove is so minute that Professor
-Nuttall and I and others for some time took it to be a closed tube.
-It receives at its base the products of the salivary glands of the
-mosquito, and it is these products which contain the organisms which
-cause malaria—a disease which has probably caused more trouble and has
-played a greater part in the history of the world than any other malady
-to which humanity is heir. Down this minute, microscopic groove has
-flowed the fluid which has closed the continent of Africa for countless
-centuries to civilisation, and which has played a dominating part in
-destroying the civilisations of ancient Greece and of Rome.
-
-When the adult mosquitos (the imagines) leave their pupa-cases they are
-unable to pierce the human skin until the mouth parts have hardened,
-and this takes at least six hours. In England they can undoubtedly
-feed twenty-four hours after leaving the pupa-case. When feeding,
-both the sensory antennae and the tactile maxillary palps are thrust
-forward at right angles to the proboscis. They thus test the place
-where the two-lobed extremity of the labium will guide the battery of
-stylets into the substance they are feeding on. The female is much more
-voracious than the male, which, as we have mentioned above, cannot
-pierce the human integument, and has to be content with a vegetarian
-diet. Sometimes the effort even of the female mosquito to insert its
-proboscis is fruitless, and we have watched a mosquito attempt four
-times to pierce the skin before it drew blood. If undisturbed during
-the meal the suctorial repast may last some two or three and a half
-minutes. So greedy at times is the mosquito that she resembles Baron
-Munchausen’s horse after the adventure with the portcullis—what is
-flowing in at one end is flowing out at the other. In fact, as Dr.
-Johnson said of the boys at a school ‘where discipline was maintained
-without recourse to corporal punishment,’ ‘But, sir, what they gain
-at one end they lose at the other!’ After the process of biting, of
-sinking-in of the piercing needles, is complete, the proboscis is
-withdrawn, and to do this the mosquito braces herself on her legs and
-raises her body.
-
-Another curious feature about the head of _Anopheles_ is that it is
-pierced by two chitinous, symmetrical tunnels—tubes which are open at
-each end with trumpet-shaped orifices. The use of these is probably to
-act as a stay or strut to strengthen the chitinous exoskeleton of the
-head; but these queer galleries or tubes also to some extent act as
-attachments for muscles.
-
-The antennae vary very much in the two sexes. In the female there
-are fifteen segments, each bearing a ring of hairs, but of small and
-disproportionate size, whereas in the male the bushy character of the
-hairs is conspicuous even to the naked eye. In fact, it is the easiest
-criterion for judging the sex of the insect. At the base of the first
-joint of the male antenna is a deep cup-shaped structure packed with
-sense organs, and containing a large nerve ganglion. There are sixteen
-segments in the whole antenna, one more than in the female. The hairs
-are capable of movement, and as a rule are kept closed on the shaft of
-the antenna whilst not in use; when evening comes on they are spread
-out. There seems little doubt that these organs are auditory and help
-the male in searching for the female.
-
-The beautiful transparent wings of the mosquito are beset with minute
-spikes, which serve to break up the light and to give rise to the
-many-coloured iridescence of the creature’s wings. The posterior border
-of the wing bears rows of beautifully graded scales. These add much
-to the symmetry and beauty of the whole structure. Just behind it are
-two balancers or halteres—a name derived from the Greek word ἁλτῆρες,
-meaning a kind of dumb-bells which athletes used in the stadium when
-jumping. These so-called balancers project outwards and backwards from
-the body when the wings are in a position of flight.
-
-A curious distinction between the _Culex_ and _Anopheles_ is in regard
-to the position assumed by the insects when they rest. In _Anopheles_
-the proboscis and body are almost in one line, and the axis of the
-body is at an angle with the surface upon which it rests. _Culex_, on
-the other hand, has its proboscis at a slight angle with its body, and
-its body is almost parallel to the surface upon which it is perching.
-_Culex_ has a much more hump-backed appearance than _Anopheles_, and
-its legs are considerably shorter and stouter. The insect generally
-rests upon four out of six legs; in the former case the hinder pair are
-held out and curved upwards. The hind legs not infrequently serve as a
-test for food. When feeding upon sweetened milk or fruit, the moment
-the hind leg touches the fluid or juice the insect will wheel round and
-at once begin to feed.
-
-_Anopheles maculipennis_ is very widely distributed, and it has been
-recorded from most parts of North America and Europe, and from many
-parts of Asia. Probably the species is much more widely distributed
-than we have any record, but individuals do not wander very far,
-of their own accord, from the breeding-places, though they may be
-dispersed by the wind. Cases are known where they have been blown as
-far as ten or even twenty miles; and in camping in Africa it is always
-well to keep to the windward of a native village. They are also
-carried about by trains, motors, and steamers. They do not indulge in
-any such voluntary migratory flights as the locusts, although some
-such flights have been from time to time recorded, but these ‘swarms’
-are probably due to a high wind catching a large number of mosquitos
-temporarily associated.
-
-In a joint paper which Professor Nuttall and I wrote some years ago, we
-drew attention to a case in which mosquitos came aboard a ship some ten
-miles from land, and to another in which a Spanish barque from Rio was
-detained in the South Atlantic quarantine station of the United States.
-The vessel was so much infested with mosquitos that it was rendered
-nearly uninhabitable, and the United States quarantine officer reported
-that when the forecastle was opened after fumigation ‘the mosquitos
-could be scooped up by hand.’ The master of the barque was positive
-that there had been no mosquitos on board until the twenty-second day
-out. Howard quotes a letter from a General living in Texas in which he
-states he has ‘twice seen flights of _Culicidae_,’ but as the species
-and the genus are not given, much of the interest of the statement
-evaporates. Generals living in Texas are not invariably remarkable for
-meticulous accuracy in recondite scientific matters.
-
-
-
-
- CHAPTER V
-
- THE MOSQUITO (_Anopheles maculipennis_)
-
- PART II
-
- There in a wailful choir the small gnats mourn
- Among the river sallows, borne aloft
- Or sinking as the light wind lives or dies.
- (JOHN KEATS, _To Autumn_.)
-
-
-The female imago hibernates. Finsch made observations and found it
-hibernating on the frozen Siberian tundras, beneath the moss and snow.
-Sterling found them in North America when the snow was melting, in
-great numbers, and he and his party were subsequently terribly bitten.
-There is no doubt that female imagines live throughout the winter, and
-they can be found in England, hibernating in cellars, old out-houses,
-chicken-houses, or disused farm buildings. These hibernating females
-disappear early in May, presumably having laid their eggs. Dr. Thayer
-of Baltimore describes these creatures, having found them on the roofs
-and walls of barns near New Orleans. Whether the male also hibernates
-is doubtful. Grassi says he never found the male of _A. maculipennis_
-in the winter, only fertilised females. But as the warm weather sets in
-the female generally becomes active and bites, and the native American
-Indians consider these elderly and famished females give more annoyance
-than at any other stage in the life-cycle of either sex. In the warmer
-climate of Southern Italy they not infrequently hibernate in grottos
-and caves. At times they occur in such numbers that they can be swept
-up. After depositing their eggs the hibernating females probably die.
-This usually happens in May.
-
-In the old days we used to collect gnats, keep them in a receptacle
-unprovided with any food, and when, after a couple of days, they died
-of starvation we wrote poems or essays on the ‘Transitoriness of Life’
-and the ‘Evanescence of Time.’
-
- The thin-winged gnats their transient time employ,
- Reeling through sunbeams in a dance of joy.
- (MRS. NORTON.)
-
-Nowadays, we feed them. Bananas, sweetened milk, pineapple, or almost
-any other vegetable juice, is their diet, and in captivity they will
-live for weeks. At Cambridge in 1900 (July to August), Professor
-Nuttall was successful in keeping females alive on a diet of bananas
-and water from two to eight weeks, but it was found essential to keep
-the atmosphere fairly moist and the food fresh. Grassi found that he
-could only keep _Anopheles_ alive in his laboratory in Rome for a month.
-
-Both _Anopheles_ and _Culex_—at any rate, in captivity—lay their eggs
-early in the morning. Apparently the nature of the food has some
-effect upon their fertility, certain observers stating that when male
-and female are fed on vegetable food alone there is no fertilisation
-and no oviposition. A diet of blood evidently assists the female to
-lay her eggs, and perhaps to get them fertilised. One of our female
-_Anopheles_ laid a batch of 146 eggs, and subsequently laid six more.
-But, as a rule, a fertilised female does not lay a second batch unless
-she receives a second meal of blood. The eggs are laid two or three
-days after the meal. There is also some evidence that a meal of blood
-is necessary if fertilisation is to be effected. As Austen says in
-_The Report of the Sierra Leone Expedition of the Liverpool School of
-Tropical Medicine_:—
-
- The following law is likely to hold good for the _Culicidae_ which
- feed on man—at least for the common species; although these gnats can
- live indefinitely on fruit, the female requires a meal of blood both
- for fertilisation and for the development of the ova. In other words,
- the insects need blood for the propagation of their species.
-
-Undoubtedly, if mosquitos ever talk, they would talk like Mr.
-Waterbrook, Mrs. Henry Spiker—Hamlet’s aunt—and the ‘simpering
-fellow with weak legs’ talked when David Copperfield dined with the
-first-named at Ely Place, Holborn. The burden of their song was: ‘Give
-us blood.’
-
-But a word of caution must be given here. Most of these deductions are
-based upon mosquitos in captivity; whether the same be true of them in
-natural conditions is not quite certain. If it be so it is difficult to
-see how these countless millions of gnats and mosquitos which dwell in
-the barren regions around the polar circle ever keep going.
-
-It very frequently happens in the Animal Kingdom that females are much
-more numerous, as well as much larger, than the males.[5] As Kipling
-tells us: ‘The female of the species is more deadly than the male,’
-but Professor Nuttall and I did not notice that this was the case with
-_Anopheles_.
-
-[5] This is a fact I have always tried to conceal from Mrs. Pankhurst;
-but, sooner or later, she is bound to find it out.
-
-There is some evidence that the male hatches out earlier than the
-female, and that in Southern Europe there may be three or four
-generations in the course of the season: the first beginning in April
-and the fourth taking place between the middle of September and the
-middle of October. After that date no larvae were found. About four
-generations also occurred in the neighbourhood of Cambridge, according
-to observations of Professor Nuttall.
-
-Kerschbaumer has calculated that if the average number of eggs laid by
-a female be 150, the number of the descendants by the fourth generation
-would amount to 31 millions. This readily accounts for the fact
-that in certain parts of the world they occur in perfectly enormous
-numbers, and if it be true that blood is essential for fertilisation
-and oviposition, very few of these potential mothers can breed. In
-nature they will feed on a great number of vegetable juices—melons,
-wild cherry-blossom, bananas, oranges, overripe mangoes; they suck
-the ‘juices’ of allied species of insects just when the imago is
-issuing from the pupa-case and before their integument is hardened,
-or they pierce the soft skin of the cicada, and occasionally attack
-the chrysalids of a butterfly. One of the most curious sources of food
-are very young trout. The adult insect attacks these _petits poissons
-filiformes_, ‘literally sucking out their unsuspective little brains
-before they could escape.’ Grassi is doubtful whether the adult males
-feed at all. He states that he never found any food in their stomach,
-nor has he ever seen a male feed. But Professor Nuttall’s experiments
-in Cambridge prove that males were seen repeatedly to feed, and to feed
-hungrily, on cherries, dried fruits, dates, and bananas.[6]
-
-[6] Owing to the recent restrictions on imported fruit imposed by the
-Government the food of these beautiful little insects will be further
-diminished. But what does our Government know or care about insects?
-
- [Illustration: FIG. 16.—View of my arm being sucked by _Anopheles
- maculipennis_ (female). (From Nuttall and Shipley.)]
-
-As mentioned before, the proboscis of the male is too weak to pierce
-the human integument, but Howard notes that it will suck up water,
-molasses, and beer; and Gray, at Santa Lucia, mentions that in that
-island _Culex_ had developed a marked fondness for port wine. One
-particularly favourite food is rose-buds covered with aphides—probably
-due to the sweetened secretion which these insects exude. The feeding
-is sometimes very ravenous, so that the insects become distended, the
-bright colour of blood, or coloured sap, readily shining through the
-joints of their chitinous armour.
-
-The reaction to heat and cold is that common to many insects. During
-the winter the imagines become torpid, quiescent, and cease to worry
-one. With returning warmth they become lively again, and generally
-wake from their winter sleep in a state of considerable hunger. They
-are insects which prefer darkness to light, and during the day-time
-congregate in caverns and grottos, under the shade of trees and bushes,
-beneath bridges, in barns, and so on. As the sun sinks they emerge from
-their hiding-places and fly during the night.
-
-Cambon, writing on _A. maculipennis_ found in the Roman Campagna, says
-that imagines ‘appear a few minutes after sunset and disappear a few
-minutes before sunrise.’ We were able to confirm this at Cambridge. The
-insects retired into the shadiest parts of the boxes in which they were
-living until the time of sunset, when a loud buzzing was heard, and the
-insects promptly fed on the food which they had neglected during the
-day. We kept our tame mosquitos in a huge gauze tent, and at night they
-invariably accumulated on the side which was illuminated by a lamp.
-Such mosquitos as were kept in a glass lamp-chimney, closed with gauze
-at each end, invariably flew towards the end which was held towards the
-light. People who are experienced with mosquitos sometimes keep the
-room in which they are sleeping dark and place a light in an adjoining
-room, leaving the door ajar, and thus lure them away. It seems a
-curious thing that, while these insects are repelled by the diffused
-light of the sun, they are attracted by the more concentrated light of
-a lamp or candle, but such is the psychology of _Anopheles_.
-
-It is not perhaps solely the influence of light; it may be the
-influence of colour; for light is very rarely entirely colourless. In
-the many experiments carried on in Cambridge on the natural history of
-the mosquito, _A. maculipennis_, not the least interesting were those
-directed to ascertaining the insect’s preference for colour. It had
-been noticed by many observers that they frequented dark-coloured areas
-rather than light: for instance, note how few mosquitos there are on
-the white collar of the gentleman in the Frontispiece compared with the
-number on his dark head and coat. Austen had pointed out that in a
-room with a dark dado it was on the dado that the mosquitos were found
-rather than on the whitened walls above. Buchanan noted that the men
-when collecting _Anopheles_ in an Indian hospital found they were to
-be most easily got by hanging up a dark coat or two upon the walls. A
-white coat they always avoided. The proverbial yellow dog of the West
-is much less bitten than the Newfoundland, and persons wearing dark
-socks and black shoes are more bitten than those who wear light ones.
-Natives, although they suffer less in health having acquired a certain
-immunity, are undoubtedly more bitten than the Europeans.
-
-The experiments we carried on at Cambridge were as follows: In the
-large gauze cubical tent in which the mosquitos were bred and kept, a
-number of pasteboard boxes without lids, measuring 20 by 16 by 10 cm.,
-were piled up. The boxes were lined with seventeen different coloured
-cloths, and were placed in rows one above another, and the order was
-changed each day, so that no question of height from the floor or
-better illumination entered into the problem. Counts were made of the
-inhabitants of each box on each of seventeen consecutive days, with the
-following results:—
-
- Average number
- Colour of box of mosquitos
- in each box.
- Navy blue 108
- Dark red 90
- Brown (reddish) 81
- Scarlet 59
- Black 49
- Slate grey 31
- Dark green (olive) 24
- Violet 18
- Leaf green 17
- Blue 14
- Pearl grey 9
- Pale green 4
- Light blue (forget-me-not) 3
- Ochre 2
- White 2
- Orange 1
- Yellow 0
- ——
- Total 512
-
-It will be noted that about the level of the pearl grey there was a
-marked drop. Pale green and pale light blue, ochre, white, orange,
-and yellow—especially the last two colours—seem positively to repel
-the insect. Our khaki-clothed soldiers have other advantages than
-invisibility to the foe. This matter is worth pursuing farther, and it
-might be possible to design mosquito-traps lined with navy-blue; by
-periodically exposing them to chloroform or benzine, or by sweeping
-out the contents, considerable numbers of mosquitos might be destroyed.
-A dark blue, sticky solution might be even more effective. After
-reading this chapter in the _British Medical Journal_, Mr. J. Cropper
-of Chepstow wrote to me as follows:—
-
- Seeing your article on Colour Selection by _Anopheles_ reminds
- me that I found the dark navy-blue lining of my tent this summer
- (in Palestine) extremely attractive to mosquitos, almost entirely
- _Anopheles_; and when the sun got hot I always noticed an increase in
- their numbers, presumably as they came from the herbage and trees near
- by. No one ever slept in the tent, and I never found _Anopheles_ bite
- in the day-time.
-
-The best way of ‘downing’ mosquitos is to prevent the imago hatching,
-and this, as has been indicated, can be done by killing the larvae and
-the pupae, which is effected by brushing oil on the water in which
-they live. The petrol or crude mineral oil should be renewed from time
-to time as it evaporates. When once the mosquitos are hatched, every
-effort should be made to keep them outside dwelling-houses by means of
-wire screens, but if that be impracticable mosquito-nets should be used
-at nights. Professor Lefroy recommends one with sixteen to eighteen
-meshes ‘to the inch.’ They may be driven away from a room by burning
-pyrethum powder in it, or vaporising cresol or carbolic acid, but of
-course this must only be done when a window is open, through which they
-can escape. As regards the human body, mosquitos may to some extent be
-kept away by smearing the skin with the various essential oils—such
-as eucalyptus oil or lemon-grass oil, &c. Mosquitos not infrequently
-bite through the socks, but wearing two pairs of socks instead of one
-pair, or inserting paper under the socks, often prevents their reaching
-the skin, as the proboscis is not long enough to penetrate two woollen
-socks, or strong enough to pierce the paper.
-
-
-
-
- CHAPTER VI
-
- THE MOSQUITO (_Anopheles maculipennis_)
-
- PART III
-
-
- The tiny-trumpeting gnat can break our dream
- When sweetest. (TENNYSON.)
-
-It is now pretty well accepted that the auditory organs of the mosquito
-are situated in the antennae. Sixty years ago Johnston of Baltimore
-was investigating the hearing-apparatus of a gnat, and came to the
-conclusion that—
-
- The animal may judge of the _intensity_ or _distance_ of the source
- of sound by the _quantity_ of the impression; of the _pitch_, or
- _quality_, by the consonance of particular whorls of stiff hairs,
- according to their lengths; and of the _direction_ in which the
- modulations travel, by the manner in which they strike upon the
- _antennae_, or may be made to meet either _antenna_, in consequence
- of an opposite movement of that part. That the male should be endowed
- with superior acuteness of the sense of hearing appears from the
- fact that he must seek the female for sexual union either in the dim
- twilight or in the dark night, when nothing save her sharp humming
- noise can serve him as a guide.
-
- [Illustration: FIG. 17.—A, _Anopheles maculipennis_, male, showing
- large, feathered antennae. B, Head of female, showing antennae with
- feathering little developed. (From Nuttall and Shipley.)]
-
-Johnston also notes that the male mosquito is the more difficult to
-catch. The bushy, complicated antennae of the male show that of the
-two sexes, with the mosquito, as with man, the male is primarily the
-hearer, the one who has to listen.
-
-Another American, Mayer, twenty years later made some interesting
-experiments confirming the views held by Johnston. He managed to cement
-with shellac a species of _Culex_ on to a glass slide, and, placing
-it beneath a low-powered microscope, watched the response of the
-antennae to tuning-forks of varying strengths. He found that under the
-influence of a fork producing 512 vibrations per second certain hairs
-of the antennae vigorously vibrated, whilst others were left unmoved.
-He measured the amplitudes of the vibrations of these hairs under the
-influence of the sound emitted by various tuning-forks. Different hairs
-were seen to vibrate to different notes. Mayer also observed that when
-the sound came from a direction in line with the long axis of the
-antennary hair vibrations ceased altogether. Hence he argued that the
-antennae could register the direction whence the sound came. Observing
-the antennae under the microscope, he confirmed the view that the
-vibrations ceased when the hairs pointed towards the source of sound,
-and on drawing a line in the direction in which the hair pointed, he
-found that it always cut within 5° of the position of the source of
-sound. He concludes:—
-
- The song of the female vibrates the fibrillae of one of the antennae
- more forcibly than those of the other. The insect spreads the angle
- between his antennae, and thus, as I have observed, brings the
- fibrillae, situated within the angle formed by the antennae, in a
- direction approximately parallel to the axis of the body. The mosquito
- now turns his body in the direction of that antenna whose fibrils are
- most affected, and thus gives greater intensity to the vibrations
- of the fibrils of the other antenna. When he has thus brought the
- vibrations of the antennae to equality of intensity he has placed his
- body in the direction of the radiation of the sound, and he directs
- his flight accordingly, and from my experiments it would appear that
- he can thus guide himself to within 5° of the direction of the female.
-
-There has always been some divergence of opinion as to how the buzzing
-sound to which the male so readily reacts is produced. Howard once
-thought that it was due to vibrations of certain chitinous processes
-in the large tracheae. Our experiments showed, however, that when the
-wing was cut off closer and closer to its origin the sound decreased in
-volume, but the note progressively rose. Unlike human beings, the male
-at all times emits a higher pitched note than the female, and in both
-sexes the note rises after feeding. ‘The greater the meal, the higher
-the note.’ This is, however, by no means confined to mosquitos. It is
-a matter which any one must have noticed when assisting at a public
-dinner or when dining in a college hall.
-
-Three unfed females gave a note of from 240 to 270 vibrations. One
-unfed female gave an abnormally low note of about 175 vibrations. Four
-other females, which were arranged in the order of the distension of
-the abdomen, after food gave notes corresponding to 264-281-297-317
-vibrations; whereas three unfed males all gave exactly the same note
-corresponding to 880 vibrations. The explanation of the higher note
-of the males is probably that their wings are markedly narrower and
-shorter than those of the females.
-
-Whilst working at _Anopheles_ the late Mr. Edwin Wilson, the artist who
-was drawing our plates, observed at the base of the wing a structure
-which may possibly account for the tone which is so characteristic a
-feature of the buzzing. The articulation of the wing with the body is
-extremely complex. There seems to be a series of structures like minute
-knuckle-bones articulated with one another, and at the outer end of the
-series are two ribbed rods which may play some part in the production
-of the overtones. One is a chitinous bar with some fourteen or fifteen
-well-marked ridges. In certain circumstances we consider that the other
-toothed rod can rasp across the ridges of the bar below it. As the wing
-is raised and lowered it seems probable that the slightly movable rod
-would be drawn across the ridged bar.
-
- [Illustration: FIG. 18.—B, Right half of thorax of _Anopheles
- maculipennis_, Meig, with base of right wing and right halter,
- magnified about 30. A, The same magnified about 5, to show the area
- which bears the stridulator. _tb_, The teeth which rasp on the ridges
- borne by _bl_; _kn_, papillae on knob; _h_, distal end of halter;
- _scl_, chitinous thickenings. (From Shipley and Wilson.)]
-
-We have mentioned above that the mosquito’s note increased in pitch as
-the wings were shortened until a very short stump was left. As long
-as these stumps were left a note was heard, and these stumps would
-undoubtedly include the apparatus just described, for it is next
-and nighest the insertion of the wing into the body. But Dr. Nuttall
-found that when this short stump was removed all perceptible sound
-ceased, which is certainly an argument in favour of these rods and bars
-playing some part in the production of the buzzing, and in opposition
-to the view of Howard and others that the buzzing is caused by certain
-chitinous structures in the tracheae.
-
-M. J. Perez[7] has carefully gone into the question of the production
-of sound in the Diptera. He claims to have shown experimentally that
-the stigmata take no part in the production of sound. ‘Les causes du
-bourdonnement résident certainement dans les ailes.’ He, too, points
-out that if the wings are cut short the notes become more acute, until
-the _timbre_ resembles that of certain interrupters which break and
-make an electric conductor. This sound we should attribute to the
-stridulator described above. M. Perez definitely states that both in
-the Diptera and in the Hymenoptera the buzzing is due to two causes:
-‘L’une, les vibrations dont l’articulation de l’aile est le siége et
-qui constituent le vrai bourdonnement; l’autre, le frottement des
-ailes contre l’air, effet qui modifie plus ou moins le premier.’ The
-apparatus we have described is, we believe, the mechanism by means of
-which the first vibrations are produced.
-
-[7] _Compt. Rend. Acad. Paris_ (1878), lxxxvii, p. 378.
-
-In the same periodical M. Jousset de Bellesme[8] confirms the statement
-that both Dipterous and Hymenopterous insects emit two sounds—one deep
-and one acute, and states that the latter is usually the octave of the
-former. It is this double note which gives rise to the peculiar buzzing
-associated with these two orders of insects. M. de Bellesme, like M.
-Perez, discards the view that acute sounds are due to any action of the
-issuing air in the stigmata, and attributes it to the vibrations of
-the pieces of the thorax which support the wing, and which are moved
-by the muscles of flight. It is usually stated that these muscles
-are not inserted into the wing, but into the sides of the thorax, to
-which the wing is so attached that when the lateral walls of this
-part of the body are deformed by the action of the muscles the wings
-move up and down. But whether this be the case or not, it is clear
-that the vibrations of the sides of the thorax caused by the muscles
-of flight—and causing the vibrations of the wing—will synchronise in
-number with these wing vibrations, and will give forth the same note.
-The existence of the higher note —‘usually the octave’ of the one
-produced by the wing vibrations—is unexplained by this view. It is,
-however, easily explicable if such a stridulating organ as we have
-described at the base of the wing in _Anopheles maculipennis_ be found
-in other Diptera and in Hymenopterous insects.
-
-[8] _Compt. Rend. Acad. Paris_ (1878), lxxxvii, p. 535.
-
-In our paper Mr. Wilson and I thought it well to figure the upper
-surface of the halter as seen under a high magnification. The drawing
-showed the hinge on which the halter quivers—and certain basal
-papillae, as Weinland[9] calls them. There is little doubt that the
-main function of the halteres is that of balancing and orientating the
-insect. They may, however, have a secondary function; in some flies
-they are known to vibrate with extreme rapidity. It is just possible
-that in these rapid vibrations the papillae of the concave surface
-rubbing against those of the convex basal plate may produce a note.
-As long ago as 1764 von Gleichen-Russworm[10] observed that when the
-halteres of the common house-fly are removed the volume of the buzzing
-diminished. This, however, in all probability is due to the diminished
-activity of the wings. On the other hand, Professor J. Stanley Gardiner
-informs us that he has noticed that mosquitos still continue to give
-forth a faint note even when their wings are quite at rest, and this
-note may possibly be caused by the halteres.
-
-[9] _Zeit. f. wissensch. Zool._ (1891), li, p. 55.
-
-[10] _Geschichte der gemeinen Stubenfliege._ Nuremberg, 1764.
-
-The part which sound plays in the life of the mosquito has not been
-very fully recognised. Grassi says that people who are talking are
-more liable to be bitten by _Anopheles_ than people who are silent—and
-quite properly, we think; people are apt to talk too much, especially
-in trains. Joly observes in Madagascar that mosquitos are attracted by
-music. When he played a stringed instrument the quiescent mosquitos in
-his room began to fly about, and if the windows were open mosquitos
-were attracted from the outside into his room, and he notes that
-mosquitos are attracted by musicians when at work, or should we say—at
-play?
-
-Two curious instances—one recorded by Howard and the other printed
-in a letter to _The Times_—of the attraction that electric buzzings
-have on these insects may be given. Mr. A. de P. Weaver, an electrical
-engineer, of Jackson, Miss., U.S.A., records that, when engaged in
-some experiments in harmonic telegraphy, he observed that when the
-note was raised to a certain number of vibrations per second, all the
-mosquitos—not only in the room, but from the outside—would congregate
-near the apparatus, and were, in fact, precipitated from the air
-with a quite extraordinary force, hurling their frail bodies against
-the buzzing machinery. This machinery formed, in conjunction with
-sticky fly-paper, an excellent means of capturing them. Mr. Weaver
-then devised a means of electrocuting the pests. He used a section
-of unpainted wire screen mounted on a board with pins driven through
-the meshes, the heads of the pins being flush with the surface of
-the screen. The bodies of the pins were then electrically connected
-together, the whole forming one electrode of the secondary coil of an
-induction coil, whilst the wire screen formed the other electrode. An
-alternating current of high potential was passed, and when the note
-was sounded the insects precipitated themselves to their doom, being
-electrocuted the moment they touched the apparatus.
-
-A somewhat similar story is told by Sir Hiram Maxim in _The Times_ of
-October 29, 1901. One of the lamps in an installation which was put
-up in Saratoga Springs, New York, hummed in an agreeable manner, and
-he noticed that night after night this lamp was covered with small
-insects. On closer examination he found that they were all mosquitos,
-and all males.
-
-
-
-
- CHAPTER VII
-
- THE MOSQUITO (_Anopheles maculipennis_)
-
- PART IV
-
- Gnats are unnoted wheresoe’er they fly,
- But eagles gazed upon with every eye.
- (SHAKESPEARE, _Rape of Lucrece_.)
-
-
-The eggs of the mosquito are deposited in fresh water, and at first
-they are white, but they very rapidly darken until they assume a
-polished black appearance. Each egg is 0·72 mm. in length, and its
-greatest breadth, which is somewhere about its middle, is 0·16 mm. The
-egg is boat-shaped, and one end, as is usual in boats, is slightly
-deeper and fuller than the other. The under surface is fluted, and
-is marked by a minute network. The upper surface has a coarser
-reticulation which divides the surface into nearly equal hexagonal
-areas. The rim of the ‘boat’ is thickened, and these thickenings are
-regularly ribbed; they extend over above the median third of the egg,
-and recall the rounded float which runs along the edge of a life-boat:
-and indeed they serve the same purpose, for they are composed of
-air-cells, and their function is to keep the boat-shaped eggs right
-side upward. Soon after the egg has been laid it is of a greyish-black
-colour, but after a certain amount of attrition an outer membrane
-splits off—the membrane which has given the egg its reticulated
-appearance. This membrane scales off in fragments, and is of a grey
-colour. The egg beneath it is glistening black—as shiny and as black as
-patent leather.
-
-One curious fact that Professor Nuttall and I noticed in the
-life-history of the egg is that when it is drawn by capillary forces
-a little way out of the water on to the leaf of a water-plant or some
-other half-submerged object, the blunt end always points downwards. Now
-the blunt end is the head end, and thus, should hatching take place
-whilst the egg is suspended half in the water and half in the air, the
-larva will emerge into its proper element and not into the atmosphere.
-
- [Illustration: FIG. 19.—Larva and eggs of _Anopheles maculipennis_.
- A, Egg seen from the side, × about 20; _fl_, the float. B, Egg seen
- from the upper surface, × about 20; _fl_, ridge of air-chambers, which
- acts as a float. C, Very young larval stage, × about 20; _st_, stigma.
- D, Fully grown larva, × about 20; _b_, brush _ant_, antenna; _mp_,
- palp of maxilla; _st_, stigma; _t_, tergum; _ap_, anal papillae. E,
- Flabellum or flap, which overhangs the base of certain thoracic hairs.
- F, A palmate hair, highly magnified. (From Nuttall and Shipley.)]
-
-Like other objects floating on the surface, the mosquito-egg slightly
-indents the surface. The number of eggs seems to vary. According to
-Grassi, each female deposits about one hundred eggs, whilst Howard puts
-the number as varying from forty to one hundred. We, however, found in
-captivity the female laid about one hundred and fifty. According to
-Grassi, the eggs of _A. maculipennis_ lie side by side like the bridges
-of boats which span the Rhine, whilst those of _A. bifurcatus_ arrange
-themselves with their ends in contact, forming starlike patterns.
-Unlike the eggs of the gnat (_Culex_) the eggs of _Anopheles_ do not
-adhere together, and the result is they are very readily scattered
-by the wind. But in sheltered places, like a laboratory aquarium, if
-undisturbed, the Italian Professor found that they tended to congregate
-together, as indeed do most minute objects floating on the surface of
-the water. Our observations did not entirely confirm those of Grassi.
-In Cambridge, at any rate, we found the eggs in our aquaria always
-scattered. Very frequently empty egg-shells were met with, but they too
-were scattered. As a rule, in nature, the ova are deposited in water
-rich with algae or other vegetable life, and they are more frequently
-in shallow than in deep water, the temperature of shallow water being
-naturally somewhat higher.
-
-On the second or third day after oviposition (and this depends upon the
-temperature), the young larva leaves the egg and begins to swim in the
-water. The egg hatches by the detachment of a cap-like portion of the
-anterior end of the egg-shell. There is no visible ring indicating the
-limits of this operculum, but the cap is usually more or less of the
-same size. Opinions differ as to how far desiccation interferes with
-development of the larva in the egg-shell. They do not seem to be able
-to stand more than forty-eight hours of drought. There is no evidence
-that they can survive throughout the winter period. Everything that we
-know indicates that the egg must pass this period within the mother’s
-body, and that they only attain maturity in early spring, when the
-weather becomes warmer.
-
-The larva of the mosquito is one of the most fascinating objects one
-can watch under the microscope. It is very complex, and consists of the
-usual arthropod regions of (1) the head, (2) the thorax, and (3) the
-abdomen.
-
- [Illustration: FIG. 20.—Side view of head of a fully grown larva of
- _Anopheles maculipennis_. _b_, Brush; _c_, antenna; _d_, palp of
- maxilla; _m_, hooked hairs at edge of maxilla; _p_, median tuft of
- hairs; _r_, thickened rim of chitinous covering to head; _s_, large,
- feathered hairs which overhang head; _t_, mandible; _u_, larval eye;
- _v_, eye of adult, forming above and behind _u_. (From Nuttall and
- Shipley.)]
-
-Without going into the question of how many typical somites make up the
-head, we must state that the thorax has the typical number of three,
-much fused together, and the abdomen nine. The first seven of these
-are very much alike; the eighth, however, bears the large stigmata or
-orifices of the breathing system, and the ninth a number of beautifully
-arranged hairs, by means of which the larva to a great extent steers
-itself. The head resembles two-thirds of a sphere, and is covered with
-a complete and clearly defined brown, chitinous case. The eyes are
-lateral, and on each side we have both a simple and a compound eye. In
-front of each eye is a little protuberance, which carries the antenna,
-and between these two eminences a band of pigment runs across the
-head, from which six symmetrically placed immovable feathered hairs
-project, wreathing the head, as it were, with a halo. There are many
-other hairs on the head, whose number and shape are of great systematic
-importance. The anterior edge of the head carries on each side of its
-under surface a conspicuous brush, very like a shaving-brush, the
-constituent hairs of which are arranged in a spiral, and it is these
-brushes which sweep the food into the mouth of the young and voracious
-larva. The base of this brush is so arranged that when depressed and
-bent towards the mouth the two brushes approximate, but each brush can
-move independently and often does so: one may be depressed towards the
-mouth, whilst the other remains erect.
-
- [Illustration: FIG. 21.—Ventral view of head of a fully grown larva
- of _Anopheles maculipennis_. _b_, Brush; _c_, antenna; _d_, palp of
- maxilla; _j_, stout hairs of mandible, which arrange the brush; _k_,
- teeth of mandible; _m_, hooked hairs at edge of maxilla; _p_, median
- tuft of hairs; _q_, the ‘underlip’ of Meinert, or metastoma; _r_,
- thickened rim which passes into the soft tissues of the neck. (From
- Nuttall and Shipley.)]
-
-The larva passes its life hanging on to the under surface of the
-surface-film of the water, its dorsal surface being uppermost. In fact,
-as Sidney Smith pointed out about the sloth, ‘it passes its life in a
-state of suspense, like a young curate distantly related to a bishop.’
-But, since these larvae feed on any kind of organic débris that
-floats up to the top and is there arrested by the surface-film, it is
-obviously important that the brushes which sweep together these organic
-particles and carry them to the mouth should be next the surface, and
-to effect this the head must rotate through an angle of 180°; and
-the head does in fact turn upside-down on the neck so sharply and
-accurately that, as it comes into position, you almost think, as you
-are watching it, that you hear a click, just as you do when you rotate
-the diaphragm of a microscope.
-
-The mouth parts now begin to vibrate upwards and forwards, and the
-brushes are bent downwards, backwards, and inwards. Round the mouth is
-a small space, the walls of which are completed by the mandibles, and
-into this space the brushes are suddenly bent back, at the same time
-the mandibles and maxillae move forward to meet them. This movement may
-take place as many as 180 times a minute, and it produces a current
-converging in concentric curves towards the above-mentioned chamber.
-The water filters out between the sides, and any particle of food is
-retained by the hairs or by the mouth appendages; from time to time
-the mandibles are brought together, and their stiff bristles are run
-through the brushes as one’s fingers run through a beard;[11] at other
-times the brushes disappear far into the mouth, and then are slowly
-withdrawn, passing through the comb-like bristles on the mandibles. The
-brushes are frequently swallowed, and are withdrawn in little jerks,
-so that the maxillae have every opportunity of combing any nutritive
-particles out of them. The whole operation is a most fascinating one to
-watch.
-
-As far as one can judge, the currents set in motion by the action
-of all these forces extend in an area equal to twice the length of
-the larva, or even more. The currents are in the plane just below
-the surface-film, and any organic matter lighter than water is swept
-towards the mouth. In fact the larva sweeps the lower side of the
-surface-film of the pond or puddle just as a careful housemaid might
-sweep spiders and flies off a ceiling with a hand-brush.
-
-The principal food-supply of the larva consists of the spores of
-fresh-water algae, diatoms, particles of _Spirogyra_, and any other
-organisms which do not penetrate the surface-film. Occasionally the
-larvae devour the decaying leaves of duck-weed (_Lemna_), and sometimes
-they attack their dead fellows.
-
-[11] If you have a beard.
-
-Grassi found the intestine of the larva to contain protozoa,
-unicellular algae, and other organic detritus. In course of time some
-object too big for the larva to swallow is brought to its mouth by the
-currents, but after a very short struggle this is rejected. The minuter
-particles accumulate in the chamber for a certain time, and then are
-swallowed by a gulp-like motion and thus pass into the oesophagus.
-
- [Illustration: FIG. 22.—A comparison between the various stages in the
- life-history of the mosquito (_Anopheles_), on the left, and the gnat
- (_Culex_), on the right.
-
- ANOPHELES CULEX
-
- _IMAGO_
- _PUPA_
- _LARVA_
- _OVA_]
-
-
-
-
- CHAPTER VIII
-
- THE MOSQUITO (_Anopheles maculipennis_)
-
- PART V
-
- Amongst aquatic larvae, the most beautiful and delicate are those of
- numerous species of gnat.—(GORING AND PRITCHARD’S _Micrographia_,
- 1837.)
-
-
-In the young larva of _Anopheles_ the head is broader and deeper than
-the thorax, but in the older larvae the segments that succeed the
-head have at least twice its diameter. It is a characteristic of true
-flies, or Diptera, that the thorax should not exhibit that separation
-into three divisions which is so usual in the less specialised
-insects—such as the cockroach and this is peculiarly true of the larva
-of the mosquito—at any rate, so far as its external structure goes.
-The abdomen of the larva consists of nine free segments; the third,
-fourth, fifth, sixth, and seventh of these bear palmate hairs on the
-dorsal or upper surface, something like hands with fourteen ‘fingers’
-spread out. These hairs adhere to the under layer of the surface-film
-of the water, and help to maintain the animal in a horizontal position
-just below that film. When the larva relaxes its hold and sinks into
-the water, it not infrequently carries with it air-bubbles enclosed by
-these fourteen ‘fingers.’
-
-The eighth abdominal segment bears the stigmata or the openings
-of the respiratory apparatus, and the ninth segment has abandoned
-the flattened and square cross-section of its predecessors, and is
-cylindrical and tapering. The posterior end of the body is cut off
-sharply. Round the posterior opening of the alimentary canal are
-four white, soft papillae, which are well supplied with tracheae and
-are capable of contracting and expanding. Above these are four very
-prominent hairs, two median and two lateral, and ventrally to the ninth
-abdominal segment is a fan-shaped arrangement of hairs springing from
-two pieces of very complicated structures. These hairs seem to act to
-some extent as a rudder, and they probably serve as an accessory organ
-of locomotion. Possibly they have also a sensory or tactile function,
-and act, as so many posterior filaments do in insects, as antennae
-‘from behind.’
-
-We have referred above to the respiratory openings, and, indeed, these
-are the key to the whole situation. Close these openings— as they
-can be closed by floating petrol or other oil on the surface of the
-water—and ‘the trick is done.’ The larvae and the pupae can no longer
-breathe, and there is thus no imago to “carry on.” In _Culex_ (the
-gnat), these respiratory orifices are borne on a long tube directing
-dorsalwards—a tube which is larger and longer than a segment of the
-body, and whose presence gives the larva the appearance of a Y with
-slightly unequal limbs. These breathing-openings are of the greatest
-complexity, but the outstanding fact is that these stigmata pierce
-through the watery film and put the respiratory system of the larva
-into communication with the atmosphere of the whole cosmos. If anything
-frightens the larva, certain side-pieces and flaps fold suddenly
-backwards and over the stigmata, the connexion through the surface-film
-is broken, and the little larva, like a German submarine when it
-sights an English battleship, darts below, frequently carrying with it
-the drop of air attached to the rim of the respiratory recess which
-surrounds the openings of the two stigmata.
-
-Not infrequently the larva ceases to lie parallel to the surface of the
-water, its palmate hairs are put out of action, and then its body hangs
-down into the water, but it still maintains its respiratory connexion
-with the outer air through these breathing-pores. From time to time
-the hairs mentioned above are brushed over by the mouth parts and
-cleaned of any débris.
-
-The larvae, when they leave the surface-film sink by their own
-weight; but they not infrequently swim actively downwards, their
-swimming action being very like that of an eel. When returning
-to the surface they are entirely dependent upon their powers of
-swimming, being slightly heavier than water. When the tail reaches the
-surface-film the larvae are at once arrested, and immediately cease
-their swimming-movements. They invariably move tail forwards, and
-the hairs which we have mentioned above at the posterior end of the
-body undoubtedly act as ‘buffers’ or ‘fenders.’ As a rule, when they
-are above, they are actively engaged in feeding; but at the bottom
-they lay inert, as though feigning to be dead. Kept in a glass beaker
-they are apt to lie with their respiratory apparatus attached to the
-concave film, which capillary attraction draws up on the surface of the
-glass. Their heads then point towards the surface of the beaker. If
-forcibly kept below—say, by submerging them under a watch-glass—they
-are frequently enabled to breathe by attaching the openings of their
-respiratory apparatus to an air-bubble.
-
-The general colour of the larva is a mottled brown, darkening where the
-chitin thickens. The older larvae are to some extent green, possibly
-due to their food; but this green colour is not by any means confined
-to the alimentary tract. After moulting, the issuing larva is a uniform
-light lavender colour, which, however, very soon darkens.
-
-A strong wind passing over a pool where _Anopheles_ eggs, larvae, or
-pupae are floating, will gradually pile them all up on the side towards
-which it is blowing. The _Anopheles_ larvae undoubtedly are braver than
-those of the _Culex_—that is to say, a disturbance which will send all
-the _Culex_ larvae scurrying to the bottom will leave the _Anopheles_
-larvae unmoved.
-
-When first hatched the larvae measure somewhere about 0·7 mm. to 0·95
-mm., but when ready to pupate they have attained the length of 7 mm.
-The rate of development is greatly influenced by the temperature, and
-a few cold days will markedly retard the larval growth. In warm sunny
-weather, larvae will pupate between the second and third week, but
-larvae taken in August (if the autumn be cold) do not attain their full
-growth until November. The young larvae undoubtedly die in considerable
-numbers, and the act of pupating is also attended with certain and
-varying dangers. Out of 834 larvae and pupae caught in Cambridgeshire,
-636 were small larvae, measuring less than 4 mm.; 181 were large
-larvae, measuring up to 7 mm. But only 17 pupae were taken. There are
-other facts which show that the larvae under natural conditions succumb
-in very considerable numbers.
-
-[Illustration: FIG. 23.—Side view of late pupal stage of _Anopheles
-maculipennis_. _f_, The stigma opening at end of trumpet-like
-projections. (From Nuttall and Shipley.)]
-
-When the larva is about to turn into a pupa it comes to rest, and now
-the thoracic regions are more swollen than ever. Soon a dorsal slit
-appears along the larval cuticle and the pupa slowly, but gradually,
-emerges through this slit and leaves the larval chitinous cuticle
-behind it. On first emerging, the pupa measures about 6·5 mm., the head
-and thorax making up one-third of this. During the last larval stage
-many of the pupal organs have been re-forming and are more or less
-visible through the cuticle. The mouth parts and limbs of the third
-stage—the future imago—show no relation to those of the larva. They
-are there enclosed in their respective sheaths, but these are quite
-independent of the larval ‘appendages.’ The respiratory trumpets,
-which, as in the larva, pierce the surface-film, are ready to act as
-breathing-organs. Whereas the larvae breathe through two stigmata
-at the posterior end of the abdomen, the pupae breathe through two
-respiratory trumpets issuing from the anterior dorsal surface, and it
-is these trumpets, together with certain palmate hairs, which support
-the pupae in the right position and put the respiratory organs at this
-stage into communication with the outer atmosphere. During the pupa
-stage _Anopheles_, like the pupa of other insects, takes no food.
-
-The pupa is something like a tadpole, with its tail bent under its
-body and flapping up and down, instead of from side to side. The whole
-pupa is enclosed in a thin semitransparent membrane, through which the
-organs of the adult can readily be seen. As it grows older its colour
-darkens. Until about the time when it will give rise to the fly, the
-pupa floats quietly at the surface, breathing through its respiratory
-trumpets. When disturbed it shows considerable activity, and it is by
-no means always easy to capture by means of a pipette. At the least
-sign of danger it darts below with a series of intermittent strokes
-and rests at the bottom of the water. Its own buoyancy brings it back
-to the surface, as, unlike the larva, it is lighter than water. Not
-only has it a certain amount of air in its tracheae, but there is a
-reservoir of air at the posterior end of the thorax which acts as a
-very efficient float. When retreating below the surface the respiratory
-trumpets usually carry down with them two minute air-bubbles.
-
-[Illustration: FIG. 24.—A, Side view, B, ventral view, of the pupa of
-a male _Anopheles maculipennis_; C and D, the same views of the female
-pupa.]
-
-The sex of the pupa can be determined by the lobes at the posterior
-end of the tail: A and B (Fig. 24) representing the male, and C and D
-the corresponding parts of the female. The duration of the pupal life
-is generally three to four days, but conditions of temperature and the
-state of the natural surroundings exert considerable influence upon
-the rate of development. Howard has pointed out that the addition of
-creosote or creosote-oil to the water in which the larvae are living
-hastens the metamorphosis into pupae, and the pupa stage is passed
-through in as short a time as fifteen hours instead of the normal
-forty-eight hours of the warm waters of the Southern States in America.
-It has also been observed that showery weather hastens the rate of
-development.
-
-When the adult mosquito is about to emerge, a certain amount of
-air is secreted under the chitinous casing of the pupa. A fine
-streak containing air appears along the back, extending between the
-respiratory trumpets and the base of the head. This central streak
-gradually passes backwards until it reaches the seventh abdominal
-segment, and then suddenly the pupa extends its abdomen so that it
-floats parallel to the surface of the water instead of being under the
-rest of the pupa’s body. The chitinous integument now splits along the
-median dorsal line, and through the slit thus made the thorax of the
-adult mosquito now protrudes. By gradually pressing its abdomen against
-the pupa-case, the body of the perfect insect is slowly but gradually
-raised above the surface of the water. The head is pulled backwards
-and upwards, and millimetre by millimetre the mouth parts, the palps,
-and antennae are withdrawn, and at first remain bent backwards beneath
-the body of the insect. Gradually the bases of the wings and the
-abdomen emerge, and soon the wings are freed and immediately flatten
-out and begin to harden. The legs and the tip of the abdomen alone now
-remain to be dealt with. At this stage the insect projects far beyond
-the anterior end of the pupa encasement, and somewhat resembles an
-exaggerated figurehead on a ship. The pupa-case is still filled with
-air, and acts as a float to support the emerging insect. At last the
-front legs are being freed, the second and third pair of legs soon
-follow, and now the insect is standing on the surface of the water
-raised on its tarsal joints, the tip of the abdomen being the last part
-to free itself from the pupa-case.
-
- [Illustration: FIG. 25.—Imago of a mosquito extracting itself from the
- pupa-case, which floats on the surface of the water. Magnified. (From
- Guiart.)]
-
-The exit of the fly is naturally a very critical period in its
-life-history, and in many cases it is fatal. The freeing process takes
-between five and ten minutes. When undisturbed the emergent fly rests
-for a time until its wings and limbs are sufficiently hardened to
-enable it to fly, or at least to walk about. Sometimes the mosquito
-takes its first flight straight from the pupa-case; at other times
-it rests awhile before taking to the air. The young imago is pale in
-colour, the thorax being brown and the abdomen transparent, with a
-greenish tinge. At first the abdomen is much longer than it is later,
-for, almost immediately after the mosquito’s exit from the pupa-case
-its abdomen begins to contract, and from its hinder end four or five
-drops of a glistening, greenish-white fluid are exuded.
-
-The newly born imagines generally take to flight between five and ten
-minutes after they have emerged, and they at once begin to darken in
-colour, and in two hours assume the normal dusky colour of the adult.
-If anything hinders the insect from properly extending its limbs
-immediately on issuing from the pupa-case, the parts harden and remain
-distorted throughout life.
-
- * * * * *
-
-Anyone who has spent a day or two in Lille or Bruges, or other towns
-in Picardy and in Southern Belgium, will understand why, as my Uncle
-Toby has it, ‘Our army swore terribly in Flanders.’ The incessant and
-tireless biting of mosquitos would make any army swear, even though
-they were ignorant—as my Uncle Toby’s army certainly was ignorant—that
-the gnats, as they called them, conveyed tertian and quartan ague. In
-Europe the trouble is a summer or early autumn trouble; but our troops
-are fighting in many tropical and sub-tropical countries, where the
-mosquitos—like the poor—are always with them.
-
-That the plague can now be checked is shown by the making of the Panama
-Canal; and that this check is due to British science is shown by the
-work on the life-history of the malarial organism, first investigated
-by Sir Ronald Ross, and later, as regards the human parasites, by
-certain Italian savants. It is also due to the public health services
-of one or two British medical officers of health in the East. _Their_
-methods have been applied and improved by those responsible for the
-elusive channel which now at times separates North from South America.
-
-We have seen that the larva and the pupa hang on to the surface-film
-of the water by means of certain suspensory hairs, and by the
-openings of their breathing-apparatus. Anything which prevents the
-breathing-tubes reaching the air ensures the death of the larva and
-pupa, and then there is no issuing adult—hence the use of paraffin on
-the pools or breeding-places. It, or any other oily fluid, spreads as
-a thin layer over the surface of the pools and puddles and clogs the
-respiratory-pores and the larvae or pupae die of suffocation.
-
-In Ismailia the disease has been reduced to an amazing extent, and
-remarkable results have followed the use of these preventive measures
-at Port Swettenham in the Federated Malay States. Within two months
-of the opening of the port in 1902, 41 out of 49 of the Government
-quarters were infected, and 118 out of 196 Government servants were
-ill. Now, after filling up all pools and cleaning the jungle, no single
-officer has suffered from malaria since July 1904, and the number of
-cases amongst the children fell from 34·8 to 0·77 per cent. The only
-melancholy feature about this wonderful alleviation of suffering, due
-to the untiring efforts of the district surgeon, Dr. Malcolm Watson, is
-that his fees for attending malarial cases dropped to zero.
-
-Thus, even ten years ago, a considerable degree of success had attended
-the efforts of the sanitary authorities—largely at the instigation of
-Sir Ronald Ross—all over the world, to diminish the mosquito-plague.
-It is, of course, equally important to try to destroy the parasite
-in man by means of quinine. This is, however, a matter of great
-difficulty. In Africa and in the East nearly all native children
-are infected with malaria, though they suffer little, and gradually
-acquire a high degree of immunity. Still, they are always a source of
-infection; and soldiers stationed in malarious districts should always
-place their dwellings to the windward of the native settlements.
-
-Knowing the cause, we can now guard against malaria; mosquito-nets and
-wire-protected windows and doors are a sufficient check on the access
-of _Anopheles_ to man. If the mosquito and man could only be kept
-permanently apart, we might hope for the disappearance of the parasite
-from our fauna. In relieving man from this world-wide pest, all genuine
-lovers of animals will rejoice that we are also relieving the far more
-serious lesions of one of the most delicate and beautiful insects that
-we know.
-
-It has always been a source of surprise to me that the great resources
-and the very evident enthusiasm of the anti-vivisection societies have
-not been turned in this direction. In the malarial parasite, we have a
-most potent vivisector of the entrails of one of the most charming and
-graceful of creatures, whose poetry of movement is hardly approached
-and never equalled by the ladies of the front row of the ballet. A
-little help, a very little help, would free these fascinating flies
-from a form of trouble far worse than that the human alternative host
-suffers. Yet, as far as I know, these societies and the societies for
-the prevention of cruelty to animals have declined to help in any
-way, and have knowingly allowed thousands of millions of animals to
-perish annually by a most painful death, and have never stretched out a
-helping hand to the fairy-like and fascinating mosquito.
-
-
-
-
- CHAPTER IX
-
- THE YELLOW-FEVER MOSQUITO (_Stegomyia calopus_)
-
- ... et nova febrium
- Terris incubuit cohors.
- (HORACE.)
-
-
-Like other branches of human activity disease has its romantic and its
-unromantic side. Nobody can regard mumps or measles as romantic. On the
-other hand, yellow fever calls up all the romance of slave-trading,
-pirates and the Spanish Main, buccaneers, maroonings and other grisly
-horrors, whose sole redeeming feature was a touch of romance. Lovers
-of pirate stories—and who are not?—will always remember their graphic
-description of Yellow Jack in the West Indies.
-
-We have probably always had disease with us since the creation of the
-world—that act of ‘_impardonnable imprudence_,’ as Anatole France calls
-it; but the first description of yellow fever only dates back to 1647,
-when an outbreak occurred in the Barbados. Then, as now, it devastated
-the shipping of the port, and was soon introduced by ships into St.
-Christopher and, later, into Guadeloupe. The following year it was in
-Cuba, and in 1655 in Jamaica, and it gradually spread throughout the
-whole of the West Indies until a century or more later it reached the
-Island of St. Thomas.
-
-One of the peculiarities of the disease is that it frequently
-disappears from a given locality for long periods of time. For
-instance, it was absent in Barbados after the first outbreak until
-1690, and when it recurred it was at first not recognised as being the
-same disease which devastated the islands forty-three years before. In
-the eighteenth century there was another break of fifty-four years, and
-similar breaks can be recorded in most of the West Indian islands.
-
-Besides the West Indies, it is at present endemic in Brazil and
-on the west coast of Africa, and is common in Mexico. Whether the
-disease arose primarily in Africa and is part of the toll the American
-continent has had to pay for the slave-trade, or whether it was brought
-to the west coast of Africa from the other side of the Atlantic, is not
-certain. It apparently appeared as a regular disease in Brazil in the
-year 1849, and from that time onwards, with the exception of one year,
-has been a permanent trouble at Rio. From time to time the disease has
-been carried to neighbouring parts of America, especially to the Gulf,
-Central America, and the northern coast of South America. It has been
-introduced more than once into Monte Video and Buenos Ayres, and has
-even penetrated up the Parana as far as Asunçion. Every few years it
-extends into the Southern States and has even reached Philadelphia and
-Boston. With the exception of an outbreak in Leghorn in 1804, European
-epidemics have been confined to Portugal, Spain, and the Balearic
-Islands.
-
-It will have been noticed that most of these outbreaks occur on the
-coast and then pass up the rivers. It is thus most probable that the
-disease is one which is brought mainly by ships. It is obviously a
-disease which must be guarded against by our troops fighting near the
-coast in West Africa, as well as such troops as are left in the West
-Indies. But, above all, it must be guarded against in relation to our
-shipping fleet and our Navy, operating off the South American coasts.
-The danger, now the Panama Canal is open, of introducing the disease
-from America to Asia is a danger that should carefully be considered.
-
-Yellow fever is a disease which requires a winter temperature of at
-least 68° F., for it is a mosquito-borne disease, and the yellow-fever
-mosquito flourishes best at about this temperature. It can be
-introduced into a new locality by the arrival of an infected mosquito,
-or by the arrival of an infected human being. In the former case the
-disease breaks out within a few days; in the latter at least ten or
-twelve days elapse before new cases arise, for, as we shall see later,
-the organism, whatever it is, that causes the fever is not capable of
-passing from the mosquito until it has been in its body for ten or
-twelve days.
-
- [Illustration: FIG. 26.—_Stegomyia fasciata._ Female, lateral view
- (magnified.) Note hump-backed outline, and also the position of the
- posterior pair of legs.]
-
-Thirty-six years ago Finlay of Havana suggested that the virus of
-yellow fever was inoculated by mosquitos; but it was not until the
-publication of the discoveries by Sir Ronald Ross and others, that
-malaria is transferred by _Anopheles_, that a thorough investigation
-of yellow fever was made. In the last year of the last century
-an American Commission, consisting of Drs. Walter Reed, Carroll,
-Agramonte, and Lazear, investigated the whole subject, and, taking
-extraordinary risks, were able to prove that the infection was not
-conveyed by contact or through the air, or from bedding or clothes
-soiled by the dejecta of yellow-fever patients, but by a mosquito of
-the genus _Stegomyia_. Whatever the virus is, it is invisible, even
-under the highest powers of the microscope. It can be filtered through
-a Berkefeld filter. It is destroyed by heating to 55° C. If the blood
-of a yellow fever patient, during the first three days, be inoculated
-into a healthy man he gets yellow fever, and it is only during the
-first three days that the blood is infective. On the other hand, the
-mosquito is incapable of transferring the disease until the unknown
-organism has been in its own body for at least ten or twelve days.
-
-The mosquito in question belongs to the species _Stegomyia calopus_
-(Blanchard), or, as it is more often called in English textbooks,
-_Stegomyia fasciata_ (Fabricius). The genus _Stegomyia_ differs from
-other _Culicidae_ in having a dark grey or black colour, whilst the
-_Culicidae_ are as a rule browner. _Stegomyia_ also has silver-white
-spots and silver glistening scales, especially on the back of the legs
-and on the abdomen. The grown-up mosquito is comparatively small, and
-very elegant. Its length is some 3 to 4 mm., but if the mouth parts be
-added is some 6 to 6½ mm. long. As is usual, the male is smaller and
-feebler than the female. When settled—as, for instance, whilst sucking
-the blood of its host—it rests upon its first four legs only, the two
-hindmost being stretched out abaft like pennants waving in the air; but
-in general it has the hump-backed appearance of _Culex_ and not the
-straight outline of _Anopheles_. The colour is greyish black, modified
-by numerous white spots and rings. There is a white rim round the eyes,
-and a very characteristic lyre-like pattern on the dorsal surface of
-the thorax. The structure of the mouth parts is much the same as that
-of any other _Culicidae_. The antennae have fourteen joints, the last
-two of which in the male are longer than the others. As is again usual,
-the antennae of the male have long brush-like hairs, organs by means of
-which they find the female. The legs are banded alternately with white
-and black rings. It is this character, indeed, which has given this
-mosquito the name of the ‘tiger-gnat.’ The wings are very iridescent.
-
- [Illustration: FIG. 27.—_Stegomyia fasciata._ Above, the larvae;
- below, the eggs. Both natural size.]
-
-The pupa of _Stegomyia_ is darker and blacker than that of _Culex_,
-and, seen from the side, the head and the thorax are somewhat more
-triangular than the same parts in _Culex_. As the pupa grows older it
-grows darker. The length of the larva is 4 to 6 mm., somewhat larger
-than that of the gnat. But, like that, it has a respiratory-tube
-stretching out from the last segment of the abdomen, almost at right
-angles to the rest of the body. This respiratory-tube is much shorter
-than that of _Culex_, but is long enough to enable the larva to hang
-obliquely down into the water. The eggs are very large. They are
-covered by a mass of small ‘cells’ containing air, and they never tend
-to form a conglomerate mass like those of _Culex_, but are laid singly,
-and remain isolated until the larvae hatch. After floating a certain
-time they usually sink to the bottom of the water. Their length may
-be about a millimetre, and their colour is almost black. When the egg
-hatches, the anterior third of the shell splits off and the larva at
-once emerges.
-
- [Illustration: FIG. 28.—Larva of _Stegomyia fasciata_ breathing on the
- surface of the water. Highly magnified.]
-
-As is so often the case with mosquitos, it is the female alone
-which bites. The male nourishes itself on plant-juices, saps, and
-so on—especially they like sugary secretions—and in the absence of
-blood the female is reduced to a similar diet. Hence _Stegomyia_ is
-comparatively common in dwellings where sweetstuffs are—bakeries,
-sugar-refineries, and so on. These mosquitos are, like the cockroach,
-the fly, and the bed-bug, inhabitants of human dwellings. They are
-indeed domesticated, and are always to be found in the neighbourhood of
-human houses or buildings or ships, and are very rarely indeed found
-far away from the sphere of man’s activities.
-
- [Illustration: FIG. 29.—Egg of _Stegomyia fasciata_ (highly
- magnified). Notice the air-‘cells.’]
-
-They are very apt to bite one in the neck, creeping along the darker
-parts of the clothing until an unprotected region of the body is
-reached. Unless one has very thick socks they frequently bite the
-ankle, and they are as tireless in their pesterings as ever Mrs.
-Pardiggle was—no sooner are they driven away than they return to the
-attack. The bite is painful, and in many people raises a considerable
-swelling.
-
-The _Stegomyia_ bite not only during the night, but also during the
-day. According to R. O. and O. Neumann—in Brazil, at any rate—they are
-capable of biting not only during the twilight, but at any times. The
-bite lasts twenty to thirty seconds, after which the mosquito rests
-a bit, waving its third pair of legs in the sun. After this rest she
-flies away to some sheltered spot, and whilst blood is being digested
-the mosquito takes nothing but water—a very proper dietetic measure.
-After three or four days the female is ready for another meal.
-
-In the absence of man these mosquitos will suck blood from other
-animals, and in confinement they are generally fed on rats or canaries,
-and they will even suck up a drop of blood presented on a piece of
-cotton-wool.
-
-If the female mosquito has been fertilised before the sucking of blood
-she will commence egg-laying two or three days later, and two or three
-days later again the larva will emerge. The larval stage lasts from
-nine to twelve days, and the pupa stage three to four, so that the
-whole metamorphosis takes from sixteen to twenty-two days. Hence,
-during warm weather, many generations succeed each other, but one must
-have a temperature of at least 20° to 27° C. Below that temperature
-the processes tend to slow down, and under a temperature near
-freezing-point the regular development is definitely interrupted. But
-the interruption is only a suspense, and living activities are resumed
-should the temperature rise again.
-
-It is a disputed point whether these mosquitos must have a meal of
-blood before they can lay eggs, and on this point the evidence is not
-yet sufficient to make a dogmatic statement. These mosquitos are very
-indifferent where their eggs are laid. The smallest collection of water
-in an empty sardine-tin, a broken tumbler, a puddle in the street, a
-gutter-pipe, is good enough for _Stegomyia calopus_. She will even lay
-her eggs on moist cotton-wool.
-
-Although _Stegomyia_ bites freely during the day-time, it, as a rule,
-avoids the light and seeks some dark shelter. Contrary to the habits
-of _Anopheles_, it prefers a light ground to rest upon. The larvae
-live on algae, vegetable-matter, or plant-detritus, or, in captivity,
-on white bread or Indian corn. They can remain for a considerable time
-without food, and this without materially diminishing the rate of their
-development. _Stegomyia_ breeds well in ships, and is occasionally
-found in one part only of the ship—such as the engine-room or cook’s
-galley, where the conditions seem to be most favourable to its
-development. Thus it comes about that at times certain quarters of a
-ship provide the greatest percentage of yellow-fever cases.
-
-
-
-
- CHAPTER X
-
- THE BISCUIT-‘WEEVIL’[12] (_Anobium paniceum_)
-
- ‘Let us be merry,’ said Mr. Pecksniff. Here he took a captain’s
- biscuit. ‘It is a poor heart that never rejoices; your hearts are not
- poor. No!’—(DICKENS, _Martin Chuzzlewit_.)
-
-The first things to notice about the biscuit-‘weevil,’ so familiar
-to readers of Marryat’s novels, is that it is not a weevil at all,
-and that it attacks a great many other comestibles besides biscuits.
-The so-called biscuit-‘weevil’ is in truth an _Anobium_—_Anobium
-paniceum_—a member of the family _PTINIDAE_ and is closely allied
-to _A. striatum_, which makes the little round holes in worm-eaten
-furniture, so cleverly imitated by the second-hand furniture-dealers.
-Another species of _Anobium_ (recently re-christened _Xestobium
-tessellatum_), a somewhat larger insect, is destructive in churches,
-libraries, and old houses. Their mysterious tappings (which are really
-efforts to attract the other sex—mere flirtations) are the cause of
-much superstitious dread in the nervous, and this species is known as
-the ‘greater death-watch.’
-
-[12] Modern systematists now call the biscuit-‘weevil’ _Sitodrepa
-panicea_.
-
- [Illustration: FIG. 30.—Biscuit-‘weevil,’ _Anobium paniceum_. (From
- David Sharp, _The Cambridge Natural History_, vol. vi.)]
-
-But to return to the biscuit-‘weevil.’ The mature insect is about a
-quarter of an inch long, and lives at large; it is the larva which
-burrows into and attacks the dried biscuit—the ‘hard-tack’ of the
-Navy. Less of a woodborer than its allies, it nevertheless attacks
-almost any vegetable substance; and Butler tells us that ‘rhubarb-root,
-ginger, wafers, and even so unlikely a substance as Cayenne pepper
-have been greedily devoured by it.’ Several generations have been
-known to flourish on a diet of opium, and it has been found in tablets
-of compressed meat. Vegetable matter, even in an altered state—such
-as paper—affords it an ample meal; and in one case the larva of
-an _Anobium paniceum_ bored steadily in a straight line through
-twenty-seven folio volumes in a public library, and so straight was the
-tunnel that a string could be passed through it from end to end. In
-one of our libraries at Cambridge some Arabic manuscripts were almost
-entirely destroyed by the larvae, which do not hesitate to browse on
-drawings and paintings and the dried paper of herbaria.
-
- [Illustration: FIG. 31.—Early stages of _Anobium paniceum_. A, Eggs,
- variable in form; B, larva; C, pupa; D, asymmetrical processes
- terminating body of pupa. This larva is probably the ‘book-worm’ of
- librarians. (From David Sharp, _The Cambridge Natural History_, vol.
- vi.)]
-
-The larva of this beetle is in truth a book-worm. Its interest for us
-in the present series is, however, the disastrous infestation of ships’
-biscuits, which frequently is so severe that the sailors ‘hard-tack’
-is rendered uneatable. Heating, of course, kills it; but the biscuits
-are still uneatable. The dead larvae are as unpalatable as the living.
-The contrivance of biscuit-tins since Marryat’s time has done much
-to lessen the evils. Tradition has it that a great firm and a great
-fortune had their foundations laid, during the first half of the last
-century, by the accidental contiguity of a baker’s shop and that of a
-tinsmith.
-
-
-
-
- CHAPTER XI
-
- THE FIG-MOTH[13] (_Ephestia cautella_)
-
- All’ amico mondagli il fico.
- (_Italian Proverb._)
-
-
-The extension of the War to Turkey and Asia Minor has drawn attention
-to the existence of certain insects whose larvae exercise a very
-deleterious effect on valuable food-supplies in the Near East. The
-inhabitants of Asiatic Turkey, without knowing it, have from time
-immemorial adopted the advice of Captain Cuttle: ‘Train up a fig-tree
-in the way it should go, and when you are old sit under the shade on
-it. Overhaul the—— Well,’ said the Captain, ‘on second thoughts, I
-ain’t quite certain where that’s to be found, but when found, make a
-note of.’
-
-[13] The figures illustrating this article are taken from _The Report
-of the Fig-moth in Smyrna_, Bul. 104. Bureau of Entomology, Washington,
-1911.
-
-Asia Minor may indeed be described as the fig-ground of the East, and
-anything that interferes with the fig as a food is likely to interfere
-with the well-being of our troops in Egypt and the Near East. In
-‘The Minor Horrors of War,’ I described a species of moth, _Ephestia
-kühniella_, a member of the family Pyralidae, which infests and
-destroys Army biscuits; but this other species, _E. cautella_, which
-attacks figs, is even more troublesome than the one described in the
-above-mentioned book.[14]
-
-[14] It might be well to repeat the fact that the genus _Ephestia_
-belongs to the family _PYRALIDAE_, which is by most authorities
-included in the _Microlepidoptera_. The Speaker’s sneer at the
-entomologists who work at this group (see his letter in _The Times_
-of February 2, 1916) is hardly worthy of one of the chief trustees of
-the British Museum. As a chief trustee, he must have been aware of the
-exhibit of the Microlepidoptera, _E. kühniella_, and its devastating
-action on the biscuits supplied to our soldiers by the War Office,
-which has for many months occupied a prominent position in the middle
-of the central hall of the Natural History Museum at South Kensington.
-This exhibit showed how closely the study of the Microlepidoptera is
-associated with the food-supply of our soldiers in many parts of the
-world.
-
- [Illustration: FIG. 32.—Typical Smyrna fig-orchard in Meander Valley,
- Asia Minor, whence come the best figs for export.]
-
- [Illustration: FIG. 33.—The fig-moth (_Ephestia cautella_). _a_, Moth
- with expanded wings; _b_, denuded wings showing venation; _c_, larva,
- full grown, dorsal view; _d_, two egg masses, _a_, _b_, _c_, About
- four times natural size; _d_, more enlarged.]
-
-Whoever has attentively eaten dried figs must from time to time have
-become aware that there is something very defective in their flavour,
-and on close inspection little clusters of débris will be observed
-on the outside of the dried fruit—the dejecta of the larva burrowing
-within—and numerous round holes can be detected through which the
-larvae have made their entrance. If cut open and carefully examined,
-one or two small white grubs may be found, which give the fig a
-singularly sour-bitter and most unpleasant taste. This is the larva
-of the moth, _Ephestia cautella_ which has for the last four or five
-years been attracting much attention in the Levant market. From 15 to
-50 per cent. of the figs exported from Smyrna, the great centre of the
-fig-trade, are infected with this ‘worm,’ and active steps were being
-taken before the War spread to the Near East to check its ravages. The
-moth itself is very like _E. kühniella_, but readily distinguished by
-an entomologist. Originally, it seems to have come from Asiatic Turkey,
-but by the aid of commerce it has been distributed in a broad belt
-all round the world within certain limits of temperature. Wide as its
-distribution now is, it is equally catholic in its tastes. Perhaps it
-does as much harm to the chocolate trade as to any other, attacking
-the cacao-bean as well as the prepared article; all sorts of nuts are
-infested. At one time it was thought that the oil of the nuts was the
-attraction, but the larvae flourish just as well on rice and bran, on
-dried apples, dried insects, maize, and a great variety of other more
-or less nutritive substances.
-
-But to return to the figs. So serious was the trouble felt to be in
-the American fig-market that, in 1910, the authorities at Washington
-sent Mr. E. G. Smyth of the Bureau of Entomology to investigate the
-insect in Asia Minor, where the figs come from, and from his report the
-following account is taken:—
-
- The manner of the fig-harvest is as follows: During August the
- figs are ripening on the trees, and are gradually dropping off to
- be collected from the ground and laid on strips of reeds, called
- ‘serghi,’ a yard broad; and here for two to five days they dry in
- the sun. When dried, they are packed in goats’-hair bags or woven
- willow baskets, and carried by horse or by camel to the fig-depots
- in the neighbouring villages. Here they are collected from the
- whole district, mixed together, and re-sacked for transmission by
- railroad to the coast. At Smyrna they are graded and prepared for
- the market: the better kind being either ‘layered’ or ‘pulled,’
- whilst the inferior fruits are strung on strings or exported in the
- form of a mashed cake to make the ‘strawberry’ jam of the Western
- breakfast-table.
-
- [Illustration: FIG. 34.—‘Serghi’ of reeds laid in long rows, used in
- large orchards. Over these the moths congregate by thousands at night.]
-
-Mr. Smyth’s object was first to find out at what stage the figs become
-infected by the moth, and then if possible to suggest preventive
-or remedial measures. He minutely investigated every stage in the
-preservation of figs, from the ripe fruit on the tree to the preserved
-figs in the hold on the steamer bound for New York, and the conclusion
-he came to is this: With very rare exceptions the eggs are never
-laid on the fruit whilst on the tree. The first and by far the most
-important infection is when the figs are gathered and exposed on the
-reed ‘serghi.’ Then about seven in the evening the moths begin to
-appear, and steadily increase in number as the evening wears on. The
-actual deposition of the ova cannot be observed, for the moths get
-down amongst the reeds and lay their eggs on the under surface of the
-fruit—usually in some crack or abrasion—so that the newly hatched larva
-can more easily make an entrance into the fig. From some ‘counts’ made
-at Tchifte Kaive it appears that after an exposure of one night 29 per
-cent. of figs were infested, after two nights 38·5 per cent., and after
-three nights 44·5 per cent.
-
- [Illustration: FIG. 35.—Figs packed by string method (reduced).]
-
-A second and serious source of infection is at the village depots.
-Before the figs arrive, there seem to be no specimens of the _Ephestia_
-in the buildings; but with their arrival the moth appears, and so
-favourable is the shelter from the heat and the wind, and so abundant
-is the supply of figs as sack after sack is emptied on to the floor,
-that soon the moth is more abundant in the depots than amongst the
-‘serghi,’ and the wonder is that a single fig escapes infestation.
-Fortunately, the time spent in the depots is short, often only a night;
-were it much longer, the whole crop would suffer. On their way down to
-the coast again there is little or no risk of the moth, but arriving
-at Smyrna we pick up the insect again in the ‘khans,’ where the figs
-are prepared for export, but in the larval form. Here, in August and
-September, little trace of the insect is seen, the larvae are then too
-small to emerge and pupate; but by October many full-grown larvae
-may be found on the fig-heaps or crawling up the walls; a few pupate
-inside the figs, and these probably produce the few imagines found in
-the ‘khans,’ at the port of shipping. The unpleasantness of the larvae
-crawling all about the ship greatly detracts from the pleasure of a
-voyage on a vessel laden with Smyrna figs.
-
- [Illustration: FIG. 36.—Pile of refuse-figs in a Smyrna ‘khan:’ On the
- wall, above these figs, fig-moth larvae congregate in large numbers.]
-
-With regard to preventive measures, there seems in many parts of Asia
-Minor to be two crops of figs—one in May and June and one later. The
-former produces a large, watery fig, unfit for sale. It is left to
-rot on the ground, but it serves as food for the larvae which will
-produce the myriad swarms of moths in the early autumn. Obviously
-these worthless figs should be destroyed as completely as possible.
-Equally obvious are the suggestions that the figs should be covered at
-night with some cheap covering whilst on the ‘serghi,’ and screened
-from the moth whilst in the depots, and their sojourn there should be
-as short as possible. Measures for destroying the larvae in the fig
-usually take the form of heat—either hot air, hot water, or steam.
-Each is effective, and each has certain advantages and disadvantages;
-still, the more progressive merchants of Smyrna were, before the War,
-experimenting trying to find the best means of destroying the larvae,
-and in time a uniform system will probably emerge.
-
-
-
-
- CHAPTER XII
-
- THE STABLE-FLY (_Stomoxys_)
-
- Fly! Thy brisk unmeaning buzz
- Would have roused the man of Uz;
- And, besides thy buzzing, I
- Fancy thou’rt a stinging-fly.
- Fly—who’rt peering, I am certain,
- At me now from yonder curtain:
- Busy, curious, thirsty fly
- (As thou’rt clept, I well know why)—
- Cease, if only for a single
- Hour, to make my being tingle!
- Flee to some loved haunt of thine;
- To the valleys where the kine,
- Udder-deep in grasses cool,
- Or the rushy margined pool,
- Strive to lash thy murmurous kin
- (Vainly) from their dappled skin!
- (CALVERLEY; _The Poet and the Fly_.)
-
-
-The common names for common insects in English are confusing. Not
-only are the same insects frequently known by different names on
-different sides of the Atlantic, but in many cases quite different
-insects—insects even belonging to different genera—are connoted
-by the same common name. In this respect matters are different in
-Germany: partly, perhaps, because the Germans on the whole are more
-scientifically inclined than we are, but partly, I suspect, because the
-German language lends itself more easily to express in one word—however
-long—the characteristics of any given insect.
-
- [Illustration: FIG. 37.—The Stable-fly (_Stomoxys calcitrans_).]
-
- [Illustration: FIG. 38.—_Stomoxys calcitrans_ × 5. Left antenna right
- × 1, resting position. (From Graham Smith.)]
-
-The genus _Stomoxys_ is generally called in Great Britain the
-‘stable-fly,’ but there are other ‘stable-flies.’ One of the commonest
-species of the genus is _S. calcitrans_, a two-winged muscid fly, not
-at all unlike the common domestic fly, _Musca domestica_; but there
-are one or two points which readily distinguish it from the commoner
-insect. To begin with: it has a hard, firm, chitinous, piercing
-proboscis, which when at rest stretches forward in front of the head,
-and when in action is pressed down at right angles to the longitudinal
-axis of the body; then, again, when resting, its wings diverge; those
-of the house-fly approximate. Like other flies, the _Stomoxys_ varies
-somewhat in length, between 5·5-7 mm. The thorax has on its back four
-longitudinal, dark stripes, broken by a transverse suture; and, as
-the accompanying figure shows, the third of the great, long veins
-which traverse the wing is much more slightly bent than is the case
-in _Musca domestica_. Further, whereas the hinder edge of the eye in
-the house-fly is straight that of the stable-fly is concave, and the
-antennae bear hairs on the upper side only and not above and below as
-they do in the domestic fly.
-
-As a biting-fly and a blood-sucking fly, the habits of _Stomoxys_
-naturally differ from those of _Musca domestica_; but, like the latter,
-its distribution is almost world-wide. It is found in all temperate
-and tropical countries, and extends as far north as Lapland. But it is
-perhaps most abundant (or shall we say it has been most observed?) in
-temperate climates and during the summer months.
-
- [Illustration: FIG. 39.—Wing of _Musca domestica_ above, and of
- _Stomoxys calcitrans_ below.]
-
-In any farm or country house large numbers of _Stomoxys calcitrans_ are
-found in and about the cowsheds and stables, and in warm weather the
-same is true wherever cattle are grazing in the field. Later in the
-year, at the beginning of autumn, they are frequently found indoors,
-and in some ‘fly counts’ they have furnished quite 50 per cent. of the
-flies of a country house, the remaining 50 per cent. being made up
-of many other species and genera. When resting on a vertical surface
-_Stomoxys_ generally has its head pointing upwards, whereas, as a rule,
-the house-fly rests upside down. The adult fly feeds upon any decaying
-matter; but whenever it can, it sucks the blood of vertebrates, and
-at times is a real nuisance to animals as well as human beings. So
-voracious are they that should a well-fed one be injured, the others
-immediately attack it and suck up every drop of blood which it had
-secured for its own food.
-
- [Illustration: FIG. 40.—Side view of head of _Stomoxys calcitrans_. A,
- Proboscis in resting position; B, proboscis extended. (After Graham
- Smith.)]
-
-It has often been disputed whether a meal of blood is essential to the
-female mosquito before oviposition, but it seems perfectly clear that
-the female _Stomoxys_ can produce fertilised eggs without having had a
-meal of blood.
-
-The female lays a number of white, banana-shaped eggs a few inches
-below the surface of any decaying organic matter; fermenting grass from
-the lawn, decaying garden stuff, stable manure—each forms a favourable
-nidus. The eggs are laid in a heap like those of the house-fly, each
-heap containing from fifty to seventy. The egg is 1 mm. in length and
-has a grooved side, through the thicker end of which the larva escapes
-when the egg-shell splits.
-
- [Illustration: FIG. 41.—_Stomoxys calcitrans._ Eggs. (After Newstead.)]
-
-The issuing larva is almost transparent. It not only has no head,
-but the anterior end dwindles almost to a point. When fully grown
-it attains a length of 11 mm., and the larval stage usually lasts
-from two to three weeks; but development may be retarded by adverse
-circumstances up to eleven or twelve weeks, and in such cases the
-full-grown larvae are often stunted in size. In these circumstances
-the pupae they produce are markedly smaller than those which have
-followed a more normal course of development. As is true of the egg
-and of the larva, the pupa resembles the pupa of the house-fly, being
-barrel-shaped and of a chestnut-brown colour; it is 5 to 5·5 mm. in
-length. The pupa stage lasts from nine to thirteen days, but this
-period is prolonged by cold.
-
- [Illustration: FIG. 42.—Acephalous larva of _Stomoxys calcitrans_.
- (After Newstead.)]
-
-On emerging from the pupa-case the insect has to push its way to the
-surface of the rotting vegetation in which it has been produced.
-This it does partly by the alternate inflation and deflation of the
-so-called ‘frontal sac,’ and by actively pushing forward the body by
-means of its legs. Once on the surface the insect begins to clean
-itself, pumps air into its body, forces it along the tracheae in
-the wings, which expand and ultimately harden. In the processes of
-unfolding they are aided by the hind legs. For a time the insect is
-immobile, gradually stiffening; but when the integument has hardened it
-flies off to explore the outer world. Under normal conditions the whole
-life-cycle varies from twenty-seven to thirty-seven days.
-
-The chief interest of _Stomoxys_ to the public, rests upon the fact
-that it is a very potent carrier of disease. There are certain forms
-of _Trypanosoma_ which, under experimental conditions, are undoubtedly
-transferred by this species. But opinion is still unsettled as
-to whether the transference of these protozoa occurs in nature.
-The _Surra_ diseases of horses and camels is, according to some
-authorities, transferred by _Stomoxys_, and so is the _Surra_ disease
-of cattle; and there are others, all fully set forth in Mr. Hindle’s
-work on ‘Flies and Disease.’
-
- [Illustration: FIG. 43.—Coarctate pupa of _Stomoxys calcitrans_.
- (After Newstead.)]
-
-Certain thread-worms—for instance, _Filaria labiato-papillosa_—which
-occur in the peritoneal cavity, and sometimes in the eyes of cattle
-and deer in India, are undoubtedly conveyed by _Stomoxys calcitrans_.
-The superficial vessels of the cattle swarm with the larvae of these
-thread-worms, which readily pass through the proboscis of the insect
-into its stomach. They then wriggle through the walls of the stomach
-and make their way into the thoracic muscles; here they undergo a
-‘rest-cure,’ and after a time they are readily transferred to a new and
-possibly uninfected host.
-
-But by far the worst infection which is attributed to this fly is acute
-epidemic poliomyelitis, or infantile paralysis. That this disease
-occurs in epidemics has been known—especially in Scandinavia—for some
-time; and eight years ago it attracted serious attention in North
-America and in our country. In 1907 there were many local outbreaks in
-the United States and Canada, and it is thought that the infection was
-first introduced from Scandinavia along the Atlantic coast, and later,
-inland, as far as the State of Minnesota, by the numerous Scandinavian
-immigrants that settle there.
-
-The disease is one of those which are apparently due to a protozoon too
-small to be visible under the highest power of the microscope, and so
-small as to be able to pass through a Berkefeld filter. It can readily
-be artificially transmitted to monkeys. It is thought that the disease
-is by no means transmitted only by means of the biting _Stomoxys_, and
-that it may be directly transmitted from one person to another without
-the aid of any intermediate host. But there seems little doubt that it
-can be, and is, transmitted by _Stomoxys_, and therefore it is of the
-highest importance to reduce the number of these insects.
-
-The most efficient way of controlling this pest is to destroy or put
-out of action its breeding-places. All decaying vegetable matter should
-be either removed or burnt or buried, or covered with some agent which
-will prevent the larvae living. In fact, the methods that have been
-advocated for the common house-fly are applicable to _Stomoxys_. If
-stable manure were carefully removed, from May to October, at least
-every seven days, the number of flies would be materially reduced.
-Where this is impracticable, manure-heaps should be covered with
-some insecticide, so as to destroy the eggs and larvae. Experiments
-are still being made with the view of finding a substance capable
-of killing the eggs, larvae, and pupae, which will be at once cheap
-and unharmful to the fertilising value of the manure. The American
-experts recommend borax or colemanite (crude calcium borate), calcined,
-powdered, and applied by a flour-dredger. The proportions which seem
-most effective are 0·62 lb. of borax and 0·75 lb. of colemanite to
-10 cubic feet, or 8 bushels of manure. Two or three gallons of water
-should then be sprinkled over the manure-heap.
-
-
-
-
- CHAPTER XIII
-
- RATS[15] (_Mus_ or _Epimys_)
-
- Now, Muse, let’s sing of rats!
- (GRAINGER.)
-
-
-The overwhelming majority of rats fall under two species: (i) _Mus
-rattus_, the black rat, and (ii) _Mus decumanus_, the brown rat. The
-original home of both species is, according to Dr. Blandford, Mongolia;
-but the date of their first appearance in our islands is a matter of
-some uncertainty. According to Helm, _M. rattus_ passed into Europe
-at the time of the _Völkerwanderung_, and doubtless accompanied the
-migrating Asiatic hordes on their journeys westward. The name rat
-appears in early High-Dutch glossaries, it is mentioned by Albertus
-Magnus, and occurs in early Anglo-Saxon writings in England. This
-evidence is, however, not conclusive that in those times the rat had
-entered Great Britain; indeed, according to Bell,[16] the black rat
-was not known here until before the middle of the sixteenth century:
-at least, he says, no author more ancient than that period has
-described, or even alluded to, it as being in Great Britain, Gesner
-being the first to do so. Jenyns, in his ‘Manual of British Vertebrate
-Animals,’[17] describes _M. rattus_ as ‘truly indigenous’; but this is
-in comparison with the brown rat, whose comparatively recently arrival
-he chronicles. _M. rattus_ is said to have been common on the continent
-of Europe in the thirteenth century.
-
-[15] The modern systematist now calls the black rat _Epimys rattus_,
-and distinguishes two varieties—_E. rattus alexandrinus_ and _E. rattus
-rattus_; the brown rat is now _E. norvegicus_.
-
-[16] _A History of British Quadrupeds_, 2nd ed. London, 1874.
-
-[17] London, 1833.
-
- [Illustration: FIG. 44.—_Mus rattus._ (From Pennant.)]
-
-_M. rattus_ has, as a rule, greyish-black fur above, ash-coloured
-below, with a tail a little longer than the body and head. It is
-smaller and more elegantly built than the brown rat; its snout is
-longer and more slender, and the long, thin, scaly tail is about eight
-or nine inches in length. The British forms average in length seven
-inches from the tip of the nose to the origin of the tail. Although
-known as the black rat, its bluish, or greyish-black colour is, both in
-the East and in Northern America, frequently replaced by brown on the
-upper surface, and by white fur on the lower, or by a yellowish-brown
-rufous colour. The ears, feet, and tail are black. When kept as
-pets—and they frequently are—white and piebald varieties are often
-bred. The ears are larger in proportion than in _M. decumanus_, the
-rings of scales on the tail better marked, and spines in the fur are
-not uncommon.
-
-The black rat, or Old-English rat, begins to breed under the age of
-one year, and goes with young six weeks; it breeds frequently during
-the year, but does not commence in Bombay, according to the Plague
-Commission, until it has attained the weight of at least 70 grammes.
-In India they breed all the year round. In Britain they produce six
-to eleven young at a time; in India the average is 5·2; the largest
-number found by the Plague Commission having been nine. In Bombay it
-is noteworthy that in both species the percentage of young rats to
-the total rat population is greater during the warmer months—from June
-to October—than at other times of the year. It is also noteworthy that
-the fall in fertility begins before the onset of the plague epizootic,
-though, later, it roughly coincides with it. In Britain they increase
-so fast as to overstock their abode, and thus they are forced, from
-deficiency of food, to devour one another, and this alone, Pennant
-thinks, ‘prevents even the human race from becoming a prey to them, not
-but there are instances of their gnawing the extremities of infants in
-their sleep.’
-
- [Illustration: FIG. 45.—Head of _Mus rattus_. (From Flower and
- Lyddeker.)]
-
-The black rat is catholic as to its diet, omnivorous, and it devours
-every kind of human food. It is more domesticated than its congener,
-more devoted to human habitations, and it does immense damage to stored
-grain, seeds, and cereals. It is a better climber than _M. decumanus_,
-which accounts for its being _par excellence_ the ship-rat, since it
-can climb hawsers and more readily ‘comes on board.’ It makes its way
-up to the higher rooms of the tenement houses in Indian cities, where
-it nests and breeds undisturbed by the human inhabitants.
-
- Day by day we passed them—
- Met them unaware,
- Shambling through the lobbies,
- Squatting on the stair.
-
- Not a rat among them
- Moved to give us place,
- Staring with its cruel eye
- And its aged face.
- (F. LANGRIDGE.)
-
-Pennant[18] draws attention to the harm the black rat causes by gnawing
-and devouring not only edibles, but paper, cloth, water-pipes, and even
-furniture. In England it makes a lodge—either for the day’s residence
-or a nest for its young—near a chimney, and ‘improves the warmth by
-forming in it a magazine of wool, bits of cloth, hay, or straw.’ In
-the East it nests in the indescribable rubbish and ‘unconsidered
-trifles’ the natives accumulate in their rooms, and is seldom, if ever,
-interfered with.
-
-[18] _British Zoology._ London, 1812.
-
-Its climbing-habits enable it to ascend trees, and in India it
-frequently nests among the branches. In some tropical islands _M.
-rattus_ lives exclusively in the crowns of coco-nut palms, feeding
-almost entirely on their fruit.
-
-Contrary to the opinion of Blandford, Oldfield Thomas thinks that the
-black rat originally came from India, and thence spread all over the
-world, exterminating the indigenous rats of other countries, only to
-be exterminated later by the arrival of the stronger _M. decumanus_.
-At the present time the last-named species is not yet established in
-some countries—for instance, in those of western South America. On that
-continent, _M. alexandrinus_, a tropical variety of _M. rattus_, is
-waging war on the less highly organised native rice-rats (_Sigmodon_).
-_M. alexandrinus_ has a grey or rufous back, and a white belly.
-
-_M. rattus_ has a milder, more amenable, and tameable character
-than _M. decumanus_, and the white, or pied varieties, so dear to
-schoolboys, are of this species. It is cleanly in its habits, and the
-skin is kept in excellent order. Like other rats, it holds its food in
-its hands whilst eating, and it drinks by lapping.
-
-Although the black rat is tending to be driven out by the brown rat,
-it still lingers on in some warehouses in London, at Yarmouth, in
-Sutherlandshire, I believe in Lundy Island, and I have been told it
-occurred not so very long ago on the island in the Serpentine. It
-doubtless occurs in many other places.
-
-_Mus decumanus_, the so-called brown rat, undoubtedly comes from
-Central Asia; and at the present time there is a rat in China described
-under the name _M. humiliatus_, which is so little distinguishable from
-the brown rat that it is thought to be the parent form.
-
-The migration westward of the brown rat certainly took place much later
-than that of _M. rattus_. Its first appearance is difficult to date.
-Undoubtedly large hordes of them crossed the Volga in the year 1727,
-and continued their journey towards Central Europe. The following year,
-according to Pennant, brown rats, appeared in England—Jenyns says not
-till 1730—and almost certainly they came in ships, for on its journey
-overland it only reached Paris about the year 1750. Reaching England
-about the year of the second George’s accession, and but thirteen years
-after the first of the House of Hanover succeeded to the throne, it was
-called—probably by the adherents of the Stuart cause—the Hanoverian
-rat. It was also called the Norwegian rat—possibly from the mistaken
-idea that it reached these islands from that country. It has now passed
-to the northern half of the New World, where it is gradually driving
-out many of its weaker brethren. Its numbers are, however, kept within
-certain limits by wolves, lynxes, raccoons, coyotes, opossums, and
-other carnivora, and especially by the skunks, which enter barns and
-out-houses in search of it.
-
-Until the discovery of America, the rat and mouse were unknown in the
-New World, and the first rats who ever saw it are said to have been
-introduced in a ship from Antwerp.[19]
-
-The brown rat is of a greyish-brown colour, tinged with yellow and
-white beneath. The tail is not so long as the body. It is a larger rat
-than _M. rattus_, has shorter ears, a more powerful skull, and ten to
-twelve mammae. Its ears, feet, and tail are flesh-coloured. Like _M.
-rattus_, colour varieties occur often: the melanistic variety, not
-uncommon in Ireland, being sometimes mistaken for the black rat. It
-is a larger animal than its congener, more heavily built, with a more
-powerful head, and blunter jaws. The head and body measure some eight
-to nine inches, but the tail, as a rule, does not surpass the length of
-the body alone. Its weight averages about nine ounces. It is extremely
-fierce and extremely cunning, and in the struggle for existence with
-allied species has hitherto been consistently successful in the fight.
-
-[19] Ovalle’s ‘History of Chili,’ in _Churchill’s Voyages_, vol. iii,
-p. 45.
-
-_Mus decumanus_ is very prolific, and produces several litters a year,
-each averaging eight to ten in number, but twelve or even fourteen
-young are not very uncommonly born at one time. It begins breeding
-young—a half-grown female producing a litter of three or four; but
-in Bombay the sexes do not breed until they have attained at least a
-weight of 100 grammes. The young are naked, i.e. without hairs, and
-of a beautiful pink colour. They are blind, and their ears are gummed
-down over the auditory meatus. They are very weak and helpless, and
-need that maternal care, which, to do the female rat justice, is never
-withheld.
-
- [Illustration: FIG. 46.—_Mus decumanus._ (From Pennant.)]
-
-_M. decumanus_ is less attached to the dwellings of man than _M.
-rattus_; still, it does live in houses, though, owing to a lack of
-climbing power, it is never found above the third floor. It is largely
-a burrowing animal, and makes its nests in its burrows. _M. rattus_ can
-also burrow, but not so readily, and it nests not in the burrow, but in
-some obscure corner. A curious instance of the nesting habits of this
-species was found during the rebuilding of my ‘lodgings’ in 1911. In
-searching under the boards of the floor of the rooms of our Foundress
-the Lady Margaret, Mother of Henry VII, now the drawing-room, the
-workmen found the mummified remains of four rats, which had taken to
-themselves coverings or shrouds; and upon investigation these proved to
-consist of a vellum deed relating to the College, some paper documents
-relating to Thomas Thompson, who was Master of the College from 1510 to
-1517, and some fragments of printed matter which turned out to be part
-of an early Virgil; four leaves of a Horace; two leaves of a primer of
-Wynkyn de Worde; and finally a leaf of a work by Caxton. In addition,
-four playing-cards of the sixteenth century were found.
-
-The brown rat frequents barns, granaries, stables, slaughter-houses,
-rivers, ponds, ditches, drains, gullies, and sewers—it is, in fact,
-sometimes called the sewer-rat. It is less particular in its food than
-the black rat, which is more usually found in grain-stores. Although in
-Bombay the relative numbers of _M. rattus_ and _M. decumanus_ caught
-was as seven is to three, in open spaces, gardens, &c., the latter
-was much the commoner. Yet the report of the Plague Commission states
-that the authors ‘do not think it an exaggeration to state that every
-inhabited building in Bombay City and Island, not excepting even the
-better-class bungalows, shelters its colony of _M. rattus_.’
-
- [Illustration: FIG. 47.—Head of _Mus decumanus_. (From Flower and
- Lyddeker.)]
-
-Both species readily take to water, though _M. rattus_, being the
-better climber, more readily gets on shipboard. They will swim rivers
-and arms of the sea. The rats which infest the London Zoological
-Gardens are said to swim nightly the canal in Regent’s Park. Rats
-constantly make their way to coastal islands, and in a comparative
-short time clear the place of indigenous rabbits and birds. Puffin
-Island, off the coast of Anglesea, and the Copeland Islands, in Belfast
-Bay, are two examples of islands at one time leased for the sake of
-their rabbits to people who had to give up the lease after the rats had
-landed on them. Similar cases are known off Denmark. They greedily eat
-birds’ eggs, and are said to convey them over considerable distances,
-though how they do this is not very clear. After the destruction of
-the vertebrate land-fauna, they fall back upon the dwellers in the
-littoral, and live on prawns, shrimps, and molluscs. They are very fond
-of fish, and Lyddeker, in the ‘Royal Natural History,’ states that they
-occasionally catch and eat young eels. As their parasites show, they
-eat insects such as the meal-beetle, and when in the field they eat
-land-snails, insect larvae, and other food, which conveys into their
-bodies the same tape-worms, &c., which we find in the hedgehog and in
-the smaller carnivora.
-
-They are, in fact, omnivorous, and nothing in the way of human food
-is alien to them. They do enormous harm to corn-ricks and to stored
-grain. They are inveterate enemies of the hen-roost, the pigeon-house,
-and, as we have seen, of the rabbit-warren. When pressed by hunger,
-they readily turn cannibal, and the brown rat easily masters the black.
-There are stories of some few specimens of each species being left
-in a cage overnight; on the following morning there were only brown
-rats in that cage. To some extent they help to keep down one of the
-field-mice (Genus _Microtus_), and this is especially the case in North
-America;[20] but the benefit is doubtful since they are held to be at
-least as destructive to the crops as the field-mice, and probably more
-so.
-
-The ferocity with which they defend themselves when attacked is well
-known, and at times, when they are driven by hunger, they do not
-hesitate to attack man. They are said to nibble the extremities of
-infants, and in one—apparently authentic—instance they overcame and
-devoured a man who had entered a disused coal-mine tenanted by starving
-rats. The bite is said to be severe (they will bite through a man’s
-thumb-nail into the flesh), and the bite is long in healing.
-
-[20] ‘An Economic Study of Field-mice (Genus _Microtus_).’ By Dr.
-Lantz, in _U.S. Dept. of Agric., Biol. Survey_, Bull. 31.
-
-Rats eat much garbage and offal, and readily feed upon dead bodies.
-About sixty years ago there stood, at Monfaucon, a slaughter-house for
-horses, and this it was proposed to remove still farther from Paris. It
-is stated that the carcasses of the horses slaughtered—which sometimes
-amounted to thirty-five a day—were cleared to the bone by rats in the
-course of the following night. This excited the attention of a M.
-Dusaussois, who made the following experiment: He placed the carcasses
-of two or three horses in an enclosure, which permitted the entrance of
-rats by certain known and closable paths. Towards midnight, he and some
-workmen entered the enclosure, closed the rat-holes, and in the course
-of that night killed 2650 rats. He repeated the experiment, and by the
-end of four days had killed 9101 rats, and by the end of a month 16,050
-rats. During the process of these experiments other carcasses were
-exposed in the neighbourhood, so that in all probability M. Dusaussois
-attracted to his enclosure but a small proportion of the total
-available number of rats. All around this slaughter-house the country
-was riddled with extensive burrows, so that the earth was constantly
-falling in. In one place the rodents had formed a pathway, 500 yards
-long, leading to a distant burrow.
-
-A rat census can never be taken; but, estimating that there is one rat
-for every human being on these islands, or less than one rat for every
-acre of ground, a moderate estimate would give us 40,000,000 rats at
-any one time. It has been calculated that a rat does at least 7_s._
-6_d._ worth of damage during the course of the year: hence in Great
-Britain and Ireland, we may annually charge them with a loss of at
-least £15,000,000!
-
-From what has been said it is obvious that rats cause enormous damage
-to humanity, which is counterbalanced by the almost infinitesimal good
-they do as scavengers. I do not propose to consider in detail the harm
-they do as disease-carriers, but one cannot forget that the rat is the
-primary host of _Trichinella spiralis_, which, when conveyed from the
-rat to the pig, and—by eating uncooked or imperfectly cooked pork—from
-the pig to man, causes severe and very fatal epidemics, and enforces
-the expenditure of large annual sums on meat inspection. They further
-convey a virulent form of equine influenza from one stable to another,
-and also the ‘foot-and-mouth’ disease. But what is infinitely more
-important to man than all the other injuries put together is the harm
-they bring to suffering humanity by conveying the bubonic plague from
-one patient to another. The plague under which India and great parts of
-Burma are ‘groaning and travailing,’ is caused by a specific bacillus
-discovered in 1894 by Yersin at Hong-Kong. It flourishes in other
-vertebrates besides man and the rat, but, owing to the migratory habits
-of the latter, the rat is the most effective agent in the spread of the
-disease. Both species of rat seem about equally susceptible, and the
-presence of the microbe showed no special relation to either the age
-or the sex of either species. The microbe is conveyed from rat to rat
-and from rat to man by a flea.
-
-The destruction of the rat is now being urged on all hands, and in the
-near future we shall probably see a considerable diminution in their
-numbers in the more civilised countries of the world. This will mean
-a considerable upset in the balance of power of the almost hidden
-fauna which surrounds us on all hands. It may even, as the Medical
-Officer of Health for Bristol has pointed out, lead to an increase
-of immigration of ship-rats—those most likely to be infected by
-plague—to take up the places vacated on land by the slain. By one of
-those commercial agencies—I do not propose to go into the merits of
-any one of them—which the enterprise of our merchants is now pressing
-on the public, a large landed proprietor a few months ago completely
-freed his buildings of rats and mice. A few weeks later his house and
-out-buildings were overrun by swarms of what to him—for in the time
-of the rats and mice he had never seen one—was a new and formidable
-insect. He sought the aid of the Royal Agricultural Society, who
-referred the matter to their scientific adviser, who pronounced the
-insects to be cockroaches!
-
-Mr. H. Warner Allen, the representative of the British Press with the
-French Army, writes as follows in the _Morning Post_:—
-
- Of the smaller trench annoyances few are more worrying than the plague
- of rats. Shelters and trenches, no matter where they are made, whether
- in woods or open fields or on the mountainside, become immediately
- infested with the objectionable creatures. In one case within my own
- personal knowledge they drove a French officer out of a comfortable
- and commodious dug-out into a damp and melancholy shelter, which was
- to some extent protected from them by sheets of corrugated iron. The
- plague had attained considerable dimensions before a really organised
- attempt was made to deal with it, and there were many cases of rats
- actually biting men who were chasing them down the trenches.
-
- Terriers have proved of considerable assistance. Trains full of
- dogs have been dispatched to the Front, and poison has been fairly
- effective. Lately, a reward has been offered for every dead rat
- brought in by men in the trenches, and regular battues have been
- organised. In a single fortnight one army corps alone has disposed of
- no fewer than 8000 rats. At a halfpenny a rat this has involved an
- expense of £16, and it was certainly money well spent. The sport of
- rat-catching on such very advantageous terms has proved very popular
- among the men, who now suggest that the standing reward offered for
- the more dangerous and more exciting form of sport involved in the
- capture of a German machine-gun should be raised to a higher figure.
-
-Ferrets have been largely used in the British trenches, but their price
-is now very high, and the supply is very limited. The method which has
-had some success in combatting the rabbit-plague of Australia—killing
-all captured females and let all captured males loose—is certainly
-worth a trial. Rats will gnaw through concrete, but not if plenty of
-pieces of broken glass be mixed with the concrete. They will never
-cross a band of tar which has been kept liquid by mixing with grease.
-In the French trenches, special rat-runs are dug and these are provided
-with ‘live’ wires. On touching one of these the rat is electrocuted.
-
-In the eighteenth century, among the officers of his ‘Britannic
-Majesty,’ was an official rat-catcher, whose special uniform was
-scarlet, embroidered in yellow worsted with figures of field-mice
-destroying wheat-sheaves. Inquiry at the Lord Chamberlain’s office has
-satisfied me that the officer still exists and still catches rats, but
-I fear the uniform has been abolished. However, a book has recently
-appeared dealing officially and exhaustively with all matters of this
-kind, and as soon as I can come by it, I will look the matter up.
-Should this dignified uniform have really disappeared, might not a
-humble petition be presented that it be revived? Surely, never more
-than at the present time should the honour and glory of the rat-catcher
-be exalted!
-
-
-
-
- CHAPTER XIV
-
- THE FIELD-MOUSE (_Apodemus sylvaticus_)
-
- TO A FIELD-MOUSE
- ON TURNING HER UP IN HER NEST WITH THE PLOUGH, NOVEMBER 1785.
-
- Wee, sleekit, cowrin’, tim’rous beastie,
- Oh, what a panic’s in thy breastie!
- Thou needna start awa’ sae hasty,
- Wi’ bickering brattle!
- I wad be laith to rin an’ chase thee,
- Wi’ murd’ring pattle!
-
- I’m truly sorry man’s dominion
- Has broken Nature’s social union,
- An’ justifies that ill opinion
- Which maks thee startle
- At me, thy poor earth-born companion,
- An’ fellow mortal!
-
- I doubt na, whyles, but thou may thieve;
- What then? poor beastie, thou maun live!
- A daimen icker in a thrave
- ’S a sma’ request;
- I’ll get a blessin’ wi’ the lave,
- An’ never miss ’t!
-
- Thy wee bit housie, too, in ruin!
- Its silly wa’s the win’s are strewin’!
- An’ naething now to big a new ane
- O’ foggage green!
- An’ bleak December’s win’s ensuin’,
- Baith snell an’ keen!
-
- Thou saw the fields laid bare an’ waste,
- An’ weary winter comin’ fast,
- An’ cozie here, beneath the blast,
- Thou thought to dwell,
- Till, crash! the cruel coulter past
- Out thro’ thy cell.
-
- That wee bit heap o’ leaves an’ stibble,
- Has cost thee mony a weary nibble!
- Now thou’s turn’d out for a’ thy trouble,
- But house or hauld,
- To thole the winter’s sleety dribble,
- An’ cranreuch cauld!
-
- But, Mousie, thou art no thy lane,
- In proving foresight may be vain:
- The best-laid schemes o’ mice an’ men
- Gang aft a-gley,
- An’ lea’e us nought but grief an’ pain
- For promis’d joy.
-
- Still thou art blest, compared wi’ me!
- The present only touches thee:
- But, och! I backward cast my ee
- On prospects drear!
- An’ forward, tho’ I canna see,
- I guess an’ fear.
- (BURNS.)
-
-
-Another member of the _MURIDAE_, the field-mouse (_Apodemus
-sylvaticus_), is almost as great a nuisance in the trenches as the rat.
-The field-mouse is very like the house-mouse, with some of its features
-seen under a lens. The hind feet and ears and eyes are larger than
-are those of the house-mouse. Perhaps its much longer hind legs help
-most easily to differentiate the two species. The tail is of about
-the same length as the body and head added together, and is annulated,
-presenting some 150 rings. The hands have five-palmar pads, and the
-feet six pads. There are six mammae in the female, the anterior pair
-being pectoral.
-
-The general colour of the dorsal surface is described as wood-brown,
-which pales at the front end and towards the shoulders and flanks,
-and grows to a more reddish tinge at the posterior end. The whole
-of the lower surface is of dull, white, silvery colour, and on some
-well-developed specimens there is a spot of buff, or orange, on the
-throat, which sometimes lengthens out to form a collar. Moulting seems
-to be rare—at any rate but a few cases have been recorded.
-
-The field-mouse occurs all over Europe, and extends into parts of Asia.
-It is found all the way from Iceland, southward to Algiers, and from
-Ireland to India. In the Himalayas it has been taken at a height of
-11,500 feet, and in the mountains of Europe it frequently occurs at a
-height of 7000 feet. It is certainly the most universally distributed
-of European animals, and the number of individual specimens probably
-far exceeds that of any other mammal which occurs in its district.
-
- [Illustration: FIG. 48.—The field-mouse (_Apodemus sylvaticus_). (From
- Barrett Hamilton.)]
-
-The field-mouse does not hibernate like the dor-mouse, but is active
-and hardy at all seasons of the year. Although, like other _MURIDAE_,
-it is probably vegetarian by ancestry, it is, in effect, quite
-omnivorous. It causes considerable loss in cornfields and gardens,
-especially to early-sown peas; it eagerly eats dandelions and any
-kind of grain or nut, or berry, or fruit, or bulb, or bud. Even fungi
-have been found in their winter stores; and one family was discovered
-which had eaten considerable quantities of putty with apparently no
-deleterious effect. Their fondness for bulbs is a great nuisance to the
-Dutch tulip-merchants. As many as 300 have been trapped in a fortnight
-in a single crocus-bed. They are also a nuisance to bee-keepers,
-inasmuch as they enter the hive and eat the honeycomb, especially
-during the winter. Whilst feeding in the hedgerows, or undergrowth,
-they frequently establish themselves in birds’ nests, and occasionally
-such nests become their permanent home.
-
- In the hedge-sparrow’s nest he sits,
- When the summer brood is fled,
- And picks the berries from the bough
- Of the hawthorn overhead.
- (_Sketches of Natural History_, 1834.)
-
-They are not above sucking the birds’ eggs, or even devouring the
-young birds. They will sometimes enter disused tunnels and devour
-hibernating flies and other insects. Unlike rats, they seldom enter
-human habitations, and they are quite innocent of the peculiar odour
-which is so disagreeable in the house-mouse; and unlike the house-mouse
-and the harvest-mouse they are seldom found in stacks of corn. Their
-preference for berries explains the fact that they generally haunt
-woods and hedgerows, and their passion for growing corn accounts for
-the fact that they swarm in cornfields towards harvest-time.
-
-The field-mouse, however, does not neglect open and barren districts,
-and is found from the sea-beach to the mountain-tops. It seems to
-flourish equally well in the flower-beds of the London parks and on the
-lonely hills of Scotland. Its activities are largely confined to the
-night-time, which may account for the exceptional size of its eyes.
-It is described ‘as bounding along in a peculiar zig-zag and erratic
-manner, remotely resembling the movements of a kangaroo or jerboa.’
-Its spoor is very characteristic. The hind feet pressing nearly on the
-same spot as the fore feet, but less lightly than the latter. From time
-to time it sits upright, pricking its ears; and obviously its sense of
-hearing is very acute, for it distinguishes sounds inaudible to the
-human ear. It is mild in manner, gentle and inoffensive, extremely
-timid, and most easily trapped. It is to some extent gregarious, as
-many as fourteen or fifteen sometimes being found in the same burrow.
-
-As Fig. 49 shows, the burrow generally has an entrance which is marked
-by a little heap of excavated earth. This leads down into the nest
-where food is often stored.
-
- saepe exiguus mus
- Sub terris posuitque domos atque horrea fecit.
- (VIRGIL, _Georgics_, i. 18 b.)
-
-At the other end of the nest there are generally a couple of
-bolt-holes separated from one another by an angle of nearly ninety
-degrees.
-
- The mouse that always trusts to one poor hole
- Can never be a mouse of any soul.
- (POPE, _The Wife of Bath_.)
-
- [Illustration: FIG. 49.—Diagram of burrow of field-mouse.]
-
-The field-mouse is prolific, the female producing several litters
-throughout the greater part of the year. The mother carries the
-young-born litter about for two or three weeks, nipping the skin of her
-offspring at the side, half-way between the fore and hind legs. The
-average number of young born at one time is probably somewhere about
-five, though litters of nine are by no means unknown. All predaceous
-animals naturally eat field-mice, and they are the favourite food—at
-any rate, in some localities—of owls.
-
-
-
-
- INDEX
-
-
- Agramonte, Dr., 105
-
- Albertus Magnus, 135
-
- Allen, H. Warner, 151
-
- _Anobium paniceum_ (biscuit-‘weevil’), 111, 112
-
- _A. striatum_, 111
-
- _Apodemus sylvaticus_ (field-mouse), 153, 154
-
- _Anopheles maculipennis_, 42, 65, 106;
- head of, 49;
- distribution of, 51;
- hibernation of, 54;
- breeding habits of, 55-6;
- sensibility to light, 59;
- and colour, 60-3, 110;
- extermination of, 63;
- buzzing of, 73-4;
- eggs of, 78;
- larva, 86
-
- Austen, 55
-
-
- _Bacillus lactis aerogenes_, _B. cloacae_, 23
-
- Bell, 135
-
- Bellesme, Jousset de, 72
-
- Biscuit-‘weevil,’ 111-13
-
- Blandford, Dr., 135, 140
-
- _Blattodea_, 4
-
- Bombay Plague Commission, 137, 145
-
- Bot- or warble-fly, 25, 27;
- effect on cattle, 40;
- cure for, 41
-
- _British Medical Journal_, 24, 63
-
- Browne, Sir Samuel James, 27
-
-
- Cambon, 59
-
- Canada, 31, 32
-
- Carpenter, Prof. G. H., 36
-
- Carroll, Dr., 105
-
- _Ceratopogon_, 42
-
- _Challenger_, H.M.S., 16
-
- _Churchill’s Voyages_, 142 _n._
-
- Cropper, J., 63
-
- Cockroaches (Periplaneta), 1, 3;
- food of, 8, 11, 13, 17
-
- _Culex_, 42, 50, 51, 55, 58, 79, 88, 90, 106-7
-
-
- Duncan, P. M., 21 _n._
-
- Dusaussois, 148
-
-
- _Ectobia_, 4
-
- Elephantiasis, 47
-
- Entomology, Washington Bureau of, 114, 118
-
- _Ephestia cautella_, 114, 115, 117, 121
-
- _E. kühniella_, 115, 116, 117
-
-
- Field-mouse, 154-9
-
- Fig-moth, 114;
- ravages of, 117-22;
- prevention of infection by, 123
-
- _Filaria_, 47
-
- _Filaria rhytipleurites_, 21
-
- _Filaria labiato-papillosa_, 131
-
- Finlay (of Havana), 104
-
- Finsch, 53
-
-
- Gardiner, J. Stanley, 73
-
- Gesner, 136
-
- Gleichen-Russworm, von, 73
-
- Grassi, 54, 55, 68, 77, 78, 79, 84
-
- Gray, 58
-
-
- Hadwen, Dr., 31, 32
-
- _Halobates_, 2
-
- Helm, 135
-
- Hewitt, T. R., 36
-
- Hindle, Mr., 131
-
- Howard, 58, 71, 74, 77, 94
-
- _Hypoderma_, 25, 28
-
- _Hypoderma bovis_, 31, 32;
- eggs of, 34
-
- _Hypoderma lineatum_, 31, 32;
- eggs of, 34, 38
-
-
- Imms, Mr., 31
-
- Infantile paralysis (poliomyelitis), 132
-
- Irish Department of Agriculture, 36
-
- Ismailia, 98
-
-
- Jenyns, 136, 141
-
- Johnston (of Baltimore), 65, 66, 67
-
- Joly, 74
-
-
- Kerschbaumer, 57
-
-
- Lantz, Dr., 147 _n._
-
- Larva, of bot-flies, 28, 35;
- of mosquitos, 80-5, 90, 91, 97;
- of yellow-fever mosquito, 107;
- of stable-fly, 130
-
- Latter, 4
-
- Lazear, Dr., 105
-
- Lefroy, Prof., 63
-
- Liverpool School of Tropical Medicine, 55
-
- Lyddeker, 146
-
-
- Malaria, 48, 104;
- prevention of, 98
-
- Maxim, Sir Hiram, 75
-
- Mayer, 67
-
- Miall and Denny, 5
-
- _Microlepidoptera_, 116 _n._
-
- Morrell, Dr. C. Conyers, 21, 23
-
- Moseley, Prof., 16
-
- Mosquitos, biting apparatus, 43;
- wings, 50;
- hibernation of female, 54;
- food of, 64-7;
- experiments with, 60-3, 67-8;
- how to avoid, 63-4;
- auditory organs of, 65;
- buzzing of, 68-74;
- eggs of, 76
-
- Moufet, 3
-
- _Muridae_, 154, 156
-
- _Mus_ or _Epimys_, 135
-
- _Mus rattus_ or _Epimys rattus_, 135 _n._, 136, 139, 144, 145
-
- _M. decumanus_ or _Norvegicus_, 135 _n._, 137, 140, 141, 142, 145
-
- _M. alexandrinus_, 140
-
- _Musca domestica_, 125, 126
-
-
- Neumann, R. O. and O., 109
-
- Nuttall, Professor, 47, 52, 54, 56, 57, 58, 71, 77
-
-
- Ormerod, Miss, 28, 30
-
- _Oestridae_ (bot-flies), 28
-
-
- Pennant, 138, 139, 141
-
- Perez, J., 71, 72
-
- _Periplaneta orientalis_, 4, 5, 16
-
- _P. americana_, 4
-
- _P. germanica_, 5, 16
-
- Plague conveyed by rats, 149
-
- Port Swettenham, 98
-
- _Ptinidae_, 111
-
- Pupa of mosquitos, 92-5, 97
-
- _Pyralidae_, 116 _n._
-
-
- Rats, black, or Old-English, 137;
- brown, 141;
- ravages of 145-9;
- estimated annual damage by, 149;
- diseases conveyed by, 149;
- destruction of, 150, 152;
- in the trenches, 151
-
- Reed, Dr. Walter, 105
-
- Ross, Sir Ronald, 97, 98, 104
-
-
- Sam Browne belts, 26
-
- _Sigmodon_ (rice-rat), 140
-
- Smyrna, Report of the fig-moth in, 114 _n._
-
- Smyth, E. G., 118
-
- _Sphex_ (or _Chlorion_), 20
-
- _Spirogyra_, 84
-
- Stable-fly, 125;
- food of, 128;
- diseases conveyed by, 131, 132
-
- _Stegomyia calopus_ or _fasciata_, 101, 105;
- domesticated, 108;
- bites of, 108, 110
-
- _Stomoxys calcitrans_ (stable-fly), 125;
- distribution of, 127;
- eggs of, 129;
- diseases conveyed by, 131, 132, 133;
- extermination of, 133
-
- _Symbius blattarum_, 21
-
-
- Thayer, Dr., 53
-
- Thomas, Oldfield, 140
-
- _Trichinella spiralis_, 149
-
- _Trypanosoma_, 131
-
-
- ‘Warbled’ hides, 30
-
- Watson, Dr. Malcolm, 98
-
- Weaver, A. de P., 74, 75
-
- Weinland, 73
-
- Whelan, R. G., 37
-
- White, Gilbert, 5
-
- Wilson, Edwin, 69, 73
-
-
- _Xestobium tessellatum_, 111
-
-
- Yellow-fever, 101-3;
- localities affected by, American commission on, 105
-
- Yellow-fever mosquito, 101, 104;
- metamorphosis of, 109
-
- Yersin, 149
-
-
- AT THE BALLANTYNE PRESS
- PRINTED BY SPOTTISWOODE, BALLANTYNE AND CO. LTD.
- COLCHESTER, LONDON AND ETON
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